Document:

<PAGE>

                     ACKNOWLEDGEMENT OF ASSUMPTION OF LEASE

      ACKNOWLEDGEMENT OF ASSUMPTION OF LEASE dated as of this 28 day of June,
1999, by and among BOSTON PROPERTIES LIMITED PARTNERSHIP (as
successor-in-interest to the Trustees of 91 Hartwell Avenue Trust, "Landlord"),
MOLDFLOW PTY. LTD, an Australian corporation registered to do business in
Connecticut ("Assignor") and MOLDFLOW CORPORATION, a Delaware corporation
("Assignee").

                                 R E C I T A L S

      By Lease dated October 15, 1996 (the "Lease"), Landlord did lease to
Assignor and Assignor did lease from Landlord certain premises in the building
known as and numbered 91 Hartwell Avenue, Lexington, Massachusetts, all as more
specifically described in the Lease (hereinafter referred to as the "Premises").

      Effective as of July 1, 1999, Assignor will assign and Assignee will
assume all of Assignor's liabilities, rights and obligations under the Lease
(such assumption by Assignee being hereinafter referred to as the "Assumption").

      Landlord desires to acknowledge Assignee's assumption of Assignor's
obligations under the Lease upon the terms and conditions contained in this
Acknowledgement of Assumption of Lease (the "Acknowledgment").

      NOW, THEREFORE, in consideration of One Dollar ($1.00) and other good and
valuable consideration, paid by each of the parties hereto to the other, the
receipt and sufficiency of which are hereby acknowledged, and in further
consideration of the provisions herein, Landlord, Assignor and Assignee hereby
agree as follows:

1.    Landlord, Assignor and Assignee hereby acknowledge and agree that the
      Assumption constitutes an assignment by Assignor and an assumption by
      Assignee of Assignor's rights and obligations under Section 5.6.1 of the
      Lease.

2.    Assignee shall be directly bound and fully liable to Landlord for all of
      the obligations of Assignor under the Lease, both prior to and subsequent
      to the Assumption, including, without limitation, the obligation to pay
      rent, additional rent and all other charges in the full amount, in the
      manner and at the times provided for under the Lease.

                                      - 1 -
<PAGE>

3.    Notwithstanding the provisions of Section 5.6.6 of the Lease regarding the
      joint and several liability of Assignor and Assignee (which such
      provisions are expressly waived by Landlord in connection with this
      Assumption), Landlord hereby releases and discharges Assignor from any
      obligations and responsibilities under the Lease effective as of July 1,
      1999.

4.    Landlord's execution of this Acknowledgement shall not constitute a
      consent or acknowledgement to any future assignment of the Lease or
      subletting of the Premises which shall be subject to the terms of Sections
      5.6 through 5.6.6.

5.    All capitalized terms and words used in this instrument shall have the
      same meaning as set forth in the Lease unless a contrary meaning is
      expressly set forth herein.

6.    Except as expressly provided herein, the Lease and the terms and
      provisions thereof, shall remain unchanged and in full force and effect.

7.    This Acknowledgment may be executed in several counterparts, each of which
      shall be deemed to be an original but all of which shall constitute one
      and the same agreement.

                                      - 2 -
<PAGE>

      EXECUTED under seal as of the date and year first above written.

                                              LANDLORD

                                              BOSTON PROPERTIES LIMITED
                                              PARTNERSHIP

                                              By: Boston Properties, Inc., its
                                                  general partner

                                                  By: /s/ Stacey A. Baker
                                                      --------------------------
                                                  Name: Stacey A. Baker
                                                        ------------------------
                                                  Title: Vice President
                                                         -----------------------

                                              ASSIGNOR

                                              MOLDFLOW PTY. LTD

                                              By: /s/ Marc Dulude
                                                  ------------------------
                                              Name: Marc Dulude
                                                    ----------------------
                                              Title: Director
                                                     ---------------------

                                              ASSIGNEE:

                                              MOLDFLOW CORPORATION

                                              By: /s/ Suzanne E. Rogers
                                                  ------------------------
                                              Name: Suzanne E. Rogers
                                                    ----------------------
                                              Title: Vice President
                                                     ---------------------

                                       -3-<PAGE>

                            STOCK PURCHASE AGREEMENT

                                      among

            AMPERSAND SPECIALTY MATERIALS AND CHEMICALS III, LIMITED
                                   PARTNERSHIP,

         AMPERSAND SPECIALTY MATERIALS AND CHEMICALS III COMPANION FUND,
                               LIMITED PARTNERSHIP,

                        JTC INVESTMENT MANAGEMENT PTY LTD

                       WESTPAC CUSTODIAN NOMINEES LIMITED

                                   ------------

                          dated as of August 25, 1998

<PAGE>

                                TABLE OF CONTENTS
<TABLE>
<CAPTION>
                                                                                                 Page
                                                                                                 ----
<S>               <C>                                                                            <C>
SECTION 1.        PURCHASE OF THE SHARES; THE CLOSING...............................................1

SECTION 2.        REPRESENTATIONS, WARRANTIES OF AMPERSAND..........................................1

         2.1      Consents; Due Execution; Delivery and Performance of the Agreement................1
         2.2      Reliance on Representations and Warranties........................................2
         2.3      Investment........................................................................2
         2.4      Authority.........................................................................2
         2.5      Experience........................................................................2
         2.6      Accredited Investor...............................................................2

SECTION 3.        REPRESENTATIONS AND WARRANTIES OF THE
                  SHAREHOLDERS......................................................................2

         3.1      Title to the Shares...............................................................2
         3.2      Availability of Information.......................................................3
         3.3      Reliance on Representations and Warranties........................................3
         3.4      Absence of Success Fees...........................................................3
         3.5      Authority of JTC..................................................................3

SECTION 4.        CONDITIONS TO CLOSING.............................................................3

         4.1      Accuracy of Representations and Warranties........................................3
         4.2      Amendment to Shareholders Agreement...............................................3
         4.3      Amendment to Credit Agreement.....................................................3

SECTION 5         COVENANTS OF JTC..................................................................4

SECTION 6         SURVIVAL OF REPRESENTATIONS, WARRANTIES
                  AND AGREEMENTS; ASSIGNABILITY OF RIGHTS...........................................4

SECTION 7         MISCELLANEOUS.....................................................................4

         7.1      Notices...........................................................................4
         7.2      Entire Agreement..................................................................5
         7.3      Assignment........................................................................5
         7.4      Amendments and Waivers............................................................5
         7.5      Headings..........................................................................5
         7.6      Severability......................................................................5
         7.7      Governing Law; Consent to Jurisdiction............................................5
         7.8      Counterparts......................................................................5
</TABLE>

                                      -i-

<PAGE>

                            STOCK PURCHASE AGREEMENT

         THIS STOCK PURCHASE AGREEMENT dated as of August 25, 1998 (the
"Agreement") is made among Ampersand Specialty Materials and Chemicals III
Limited Partnership, Ampersand Specialty Materials and Chemicals Companion
Fund III Limited Partnership (collectively, "Ampersand") and JTC Investment
Management Pty, Ltd. ("JTC"), Westpac Custodian Nominees Limited (as nominee
for NJI No. 1(A) Investment Fund and NJI No. 1(B) Investment Fund ("Westpac,"
and together with JTC ,the "Shareholders").

                                 R E C I T A L S

         WHEREAS, the Shareholders are collectively the owner of shares of
Class C-1 Preferred Stock and Class C-3 Preferred Stock (the "Shares"), of
Moldflow Corporation, a Delaware corporation (the "Company") as set forth on
Exhibit A hereto;

         WHEREAS, Ampersand desires to purchase the Shares from the
Shareholders on the terms set forth herein;

         NOW THEREFORE, in consideration of the premises and of the covenants
herein contained, the parties hereto mutually agree as follows:

         SECTION 1. PURCHASE OF THE SHARES; THE CLOSING. On the Closing Date
(as hereinafter defined), the Shareholders shall sell to Ampersand, and
Ampersand shall purchase (among themselves in such proportions as ASMC-III
and ASMC-IIICF shall determine) from the Shareholders, upon the terms and
conditions hereinafter set forth, the Shares, at a price per Share of $1.46.
The closing of the purchase and sale of the Shares (the "Closing") shall take
place at a date and time as mutually agreed by the parties hereto (the
"Closing Date") at the offices of Palmer & Dodge LLP, One Beacon Street,
Boston, Massachusetts, or at such other time and place Ampersand and the
Shareholders hereto may mutually agree. On the Closing Date, each Shareholder
shall deliver to Ampersand a certificate representing not less than the
number of Shares to be transferred hereunder as set forth on Exhibit A
hereto, duly endorsed for transfer, free and clear of all liens,
encumbrances, charges or adverse claims. Upon receipt of such certificate
from each Shareholder, Ampersand shall (i) pay to such Shareholder, by cash,
certified check or wire transfer of immediately available funds to such
account as may be notified to Ampersand, the aggregate purchase price for the
Shares purchased from such Shareholder, and (ii) if the certificate delivered
by such Shareholder pursuant to this Section represents a greater number of
Shares than the Shares being transferred hereunder, promptly deliver to
Palmer & Dodge, LLP, as transfer agent for the Company, such certificate with
instructions that a balance certificate be prepared and delivered to such
Shareholder on the Closing Date.

         SECTION 2.        REPRESENTATIONS, WARRANTIES OF AMPERSAND.
Ampersand hereby represents and warrants to the Shareholders as follows:

              2.1 CONSENTS; DUE EXECUTION; DELIVERY AND PERFORMANCE OF THE
AGREEMENT. Ampersand's execution, delivery and performance of this Agreement
(a) has been duly

<PAGE>

authorized under Delaware law by all requisite corporate action by Ampersand,
(b) will not violate any law or the organizational documents or By-laws of
Ampersand or any provision of any material indenture, mortgage, agreement,
contract or other material instrument to which Ampersand is a party or by
which any of its properties or assets is bound as of the date hereof or (c)
require any consent by any person under, constitute or result (upon notice or
lapse of time or both) in a breach of any term, condition or provision of, or
constitute a default or give rise to any right of termination or acceleration
under any such indenture, mortgage, agreement, contract or other material
instrument or result in the creation or imposition of any lien, security
interest, mortgage, pledge, charge or other encumbrance, of any nature
whatsoever, upon any properties or assets of Ampersand. Upon its execution
and delivery, and assuming the valid execution thereof by the Shareholders,
the Agreement will constitute a valid and binding obligation of Ampersand,
enforceable against Ampersand in accordance with its terms, except as
enforceability may be limited by applicable bankruptcy, insolvency,
reorganization, moratorium or similar laws affecting creditors' and
contracting parties' rights generally and except as enforceability may be
subject to general principles of equity (regardless of whether such
enforceability is considered in a proceeding in equity or at law).

              2.2 RELIANCE ON REPRESENTATIONS AND WARRANTIES. Ampersand has
not received or relied on any representations or warranties of the
Shareholders other than those set forth in this Agreement.

              2.3 INVESTMENT. Ampersand is acquiring the Shares for its own
account for investment and not with a view to, or for sale in connection
with, any distribution thereof, nor with any present intention of
distributing or selling the same; and Ampersand has no present or
contemplated agreement, undertaking, arrangement, obligation, indebtedness or
commitment providing for the disposition thereof.

              2.4 AUTHORITY. Ampersand has full power and authority to
execute, deliver and perform this Agreement in accordance with its terms.
Ampersand has not been organized, reorganized, or recapitalized specifically
for the purpose of investing in the Company.

              2.5 EXPERIENCE. Ampersand has adequate net worth and means to
purchase the Shares and to provide for its current needs and contingencies
and the financial capacity to sustain a complete loss of its investment in
the Company.

              2.6 ACCREDITED INVESTOR. Ampersand is an "accredited investor"
as defined in Rule 501 of Regulation D under the Securities Act of 1933, as
amended.

         SECTION 3. REPRESENTATIONS AND WARRANTIES OF THE SHAREHOLDERS. Each
of the Shareholders hereby severally represents and warrants (except that the
representation and warranty made in Section 3.5 shall only be deemed made by
JTC) in respect to itself only, or as the case may be, the Shares to be
transferred by it to Ampersand as follows :

              3.1 TITLE TO THE SHARES. The Shareholder has good and valid
title to the Shares to be sold and transferred to Ampersand by the
Shareholder hereunder, and shall transfer such Shares to Ampersand free and
clear of all restrictions, encumbrances, liens, rights, title or

                                       2

<PAGE>

interests of others, except restrictions under applicable securities laws.
Following the purchase of the Shares by Ampersand hereunder, Ampersand will
acquire good and valid title to the Shares.

              3.2 AVAILABILITY OF INFORMATION. The Shareholder has made all
such investigations of the financial condition, business affairs and
prospects of the Company as such Shareholder deems appropriate and has
received all information requested, has consulted with personal, financial,
and legal representatives with respect to the legal, tax and other financial
effects of this transaction as such Shareholder deems necessary.

              3.3 RELIANCE ON REPRESENTATIONS AND WARRANTIES. The Shareholder
has not received or relied on any representations or warranties of Ampersand
other than those set forth in this Agreement.

              3.4 ABSENCE OF SUCCESS FEES. There are no success fees
associated with the transactions contemplated hereby that are being borne by
the Shareholders.

              3.5 AUTHORITY OF JTC. JTC has entered into this Agreement in
its capacity as the Trustee of the JTC Investment Trust and has all requisite
power and authority to act on behalf of the JTC Investment Trust and to cause
the performance by the JTC Investment Trust of the obligations of JTC
hereunder.

         SECTION 4. CONDITIONS TO CLOSING.  Notwithstanding anything else
contained herein, the obligations of each party hereunder are subject to the
satisfaction of the following conditions:

              4.1 ACCURACY OF REPRESENTATIONS AND WARRANTIES. The
representations and warranties of the Shareholders and Ampersand,
respectively, as set forth in Section 3 and Section 2 hereof, respectively,
shall be true and correct on the Closing Date as if such representations and
warranties were made as of the Closing Date.

              4.2 AMENDMENT TO SHAREHOLDERS AGREEMENT. The Second Amendment
to Shareholders Agreement, in the form attached hereto as Exhibit B, shall
have been executed by all Shareholders that are parties to the Shareholders
Agreement dated as of July 18, 1997.

              4.3 AMENDMENT TO CREDIT AGREEMENT. The First Amendment to
Amended and Restated Credit Agreement, in the form attached hereto as Exhibit
C, shall have been executed by all parties thereto.

                                       3

<PAGE>

         SECTION 5. COVENANTS OF JTC.  JTC hereby covenants and agrees as
follows:

              5.1 As soon as practicable following the Closing, JTC will use
its best efforts to redeem all of the issued units in the JTC Investment
Trust, other than (i) 50% of the units held by Tanya Lee Chambers (which
units are to be transferred by Tanya Lee Chambers to Chris Murphy), (ii) all
of the units held by Seafirst Pty Ltd. and Obena Ridge Pty Ltd., (iii) all of
the units held by PY Pty Ltd. less such number of units held by PY Pty Ltd.
which correspond to a sale of 350,000 Shares, and (iv) all of the units held
by Sentech Pty Ltd. less such number of units held by Sentech Pty Ltd. which
correspond to a sale of 30,000 Shares.

              5.2 JTC will use its best efforts to ensure that no
distribution of any securities of the Company shall be made to any holder of
equity interests of JTC until the earlier to occur of (i) an initial public
offering of any class of the Company's equity securities or (ii) any sale or
merger of the Company or a sale of all or substantially all of the assets of
the Company.

         SECTION 6. SURVIVAL OF REPRESENTATIONS, WARRANTIES AND AGREEMENTS;
ASSIGNABILITY OF RIGHTS. Notwithstanding any investigation made by any party
to this Agreement, all covenants, agreements, representations and warranties
made by Ampersand and the Shareholders herein shall survive the execution of
this Agreement, the delivery to Ampersand of the Shares being purchased and
the payment therefor. Except as otherwise provided herein, (i) the covenants,
agreements, representations and warranties of each Shareholder made herein
shall bind the Shareholder's successors and assigns and shall inure to the
benefit of Ampersand's successors and assigns, and (ii) the covenants,
agreements, representations and warranties of Ampersand made herein shall
bind Ampersand's successors and assigns and shall inure to the benefit of the
Shareholder's successors and assigns.

         SECTION 7. MISCELLANEOUS.

              7.1 NOTICES. Any consent, notice or report required or
permitted to be given or made under this Agreement by one of the parties
hereto to the other shall be in writing, delivered personally or by facsimile
(and promptly confirmed by telephone, personal delivery or courier) or
courier, postage prepaid (where applicable), addressed to such other party at
its address indicated below, or to such other address as the addressee shall
have last furnished in writing to the addressor and shall be effective upon
receipt by the addressee.

         If to Ampersand:           Ampersand Ventures
                                    55 William Street
                                    Wellesley, MA  02481
                                    Attention:  Charles D. Yie
                                    Telephone:  (781) 239-0700
                                    Telecopy:   (781) 239-0824

                                       4

<PAGE>

         with a copy to:            Palmer & Dodge LLP
                                    One Beacon Street
                                    Boston, Massachusetts 02108
                                    Attention:  Marc A. Rubenstein, Esq.
                                    Telephone:  (617) 573-0100
                                    Telecopy:   (617) 227-4420

         If to the Shareholders, at the address or telecopy number or
telephone number set forth on the signature pages hereto.

              7.2 ENTIRE AGREEMENT. This Agreement contains the entire
understanding of the parties with respect to the subject matter hereof. All
express or implied agreements and understandings, either oral or written,
heretofore made are expressly merged in and made a part of this Agreement.

              7.3 ASSIGNMENT. Neither this Agreement nor any of the rights
and obligations contained herein may be assigned or otherwise transferred by
either party without the consent of the other party.

              7.4 AMENDMENTS AND WAIVERS. This Agreement may not be modified
or amended except pursuant to an instrument in writing signed by Ampersand
and all of the Shareholders. The waiver by either party hereto of any right
hereunder or the failure to perform or of a breach by the other party shall
not be deemed a waiver of any other right hereunder or of any other breach or
failure by said other party whether of a similar nature or otherwise.

              7.5 HEADINGS. The headings of the various sections of this
Agreement have been inserted for convenience of reference only and shall not
be deemed to be part of this Agreement.

              7.6 SEVERABILITY. In case any provision contained in this
Agreement should be invalid, illegal or unenforceable in any respect, the
validity, legality and enforceability of the remaining provisions contained
herein shall not in any way be affected or impaired thereby.

              7.7 GOVERNING LAW; CONSENT TO JURISDICTION. This Agreement
shall be governed by and construed in accordance with the laws of the
Commonwealth of Massachusetts (without giving effect to the choice of law
provisions thereof) and the federal law of the United States of America.
Ampersand and each Shareholder hereby irrevocably consents to any suit,
action or proceeding with respect to this Agreement being brought in any
court of law in the Commonwealth of Massachusetts and in the United States
District Court for the District of Massachusetts and consents to personal
jurisdiction in any such court.

              7.8 COUNTERPARTS. This Agreement may be executed in two or more
counterparts, each of which shall constitute an original, but all of which,
when taken together, shall constitute but one instrument, and shall become
effective when one or more counterparts have been signed by each party hereto
and delivered to the other parties.

                                       5

<PAGE>

         IN WITNESS WHEREOF, the parties hereto have caused this Stock
Purchase Agreement to be executed by their duly authorized representatives as
of the day and year first above written.

"AMPERSAND"

SIGNED for and on behalf of AMPERSAND       )
SPECIALTY MATERIALS AND                     )
CHEMICALS III, LIMITED PARTNERSHIP          )
by its general partner ASMC III Management  )
Company LP by its general partner           )
ASMC-II MCLP LLP                            )

                                                /s/ Charles D. Yie
                                                ------------------------------
                                                By:  Charles D. Yie
                                                Its: General Partner

                                                Charles D. Yie
                                                ------------------------------
                                                Name (print)

SIGNED for and on behalf of AMPERSAND       )
SPECIALTY MATERIALS AND                     )
CHEMICALS III COMPANION FUND                )
LIMITED PARTNERSHIP by its general          )
partner ASMC IIICF Management Company LP    )
by its general partner ASMC-II MCLP LLP     )

                                                /s/ Charles D. Yie
                                                ------------------------------
                                                By:  Charles D. Yie
                                                Its: General Partner

                                                Charles D. Yie
                                                ------------------------------
                                                Name (print)

                  [Signature Page to Stock Purchase Agreement]

<PAGE>

"SHAREHOLDERS"

THE COMMON SEAL of JTC                      )
INVESTMENT MANAGEMENT PTY LTD is            )                           [SEAL]
affixed in accordance with its articles of  )
association in the presence of              )

/s/ Julian Beale                                /s/ Michael Kroger
------------------------------                  ------------------------------
Secretary                                       Director

Julian Beale                                    Michael Kroger
------------------------------                  ------------------------------
Name of secretary (print)                       Name of director (print)

Shareholder Address:
                          ----------------------------------

                          ----------------------------------

                          ----------------------------------
Telephone Number:
                          ----------------------------------

Telecopy Number:
                          ----------------------------------

THE COMMON SEAL of WESTPAC                    )
CUSTODIAN NOMINEES LIMITED (as                )
nominee for NJI No. 1(A) Investment Fund)     )
is affixed in accordance with its articles of )
association in the presence of                )

------------------------------                  ------------------------------
Secretary                                       Director

------------------------------                  ------------------------------
Name of secretary (print)                       Name of director (print)

Shareholder Address:
                          ----------------------------------

                          ----------------------------------

                          ----------------------------------
Telephone Number:
                          ----------------------------------

Telecopy Number:
                          ----------------------------------

                  [Signature Page to Stock Purchase Agreement]

<PAGE>

"SHAREHOLDERS"

THE COMMON SEAL of JTC                        )
INVESTMENT MANAGEMENT PTY LTD is              )
affixed in accordance with its articles of    )
association in the presence of                )

------------------------------                  ------------------------------
Secretary                                       Director

------------------------------                  ------------------------------
Name of secretary (print)                       Name of director (print)

Shareholder Address:
                          ----------------------------------

                          ----------------------------------

                          ----------------------------------
Telephone Number:
                          ----------------------------------

Telecopy Number:
                          ----------------------------------

THE COMMON SEAL of WESTPAC                    )
CUSTODIAN NOMINEES LIMITED (as                )
nominee for NJI No. 1(A) Investment Fund)     )      [SEAL]
is affixed in accordance with its articles of )
association in the presence of                )

/s/ Michelle Dunlop                             /s/ Sean Brennan
------------------------------                  ------------------------------
Secretary                                       Director

Michelle Dunlop                                 Sean Brennan
------------------------------                  ------------------------------
Name of secretary (print)                       Name of director (print)

Shareholder Address:                  [STAMP]
                          ----------------------------------

                          ----------------------------------

                          ----------------------------------
Telephone Number:
                          ----------------------------------

Telecopy Number:
                          ----------------------------------

                  [Signature Page to Stock Purchase Agreement]

<PAGE>

THE COMMON SEAL of WESTPAC               )
CUSTODIAN NOMINEES LIMITED (AS NOMINEE   )             [SEAL]
FOR NJI NO.1(B) INVESTMENT FUND)         )
is affixed in accordance with its        )
articles of association in the           )
presence of                              )

/s/ Michelle Dunlop                             /s/ Sean Brennan
------------------------------                  ------------------------------
Secretary                                       Director

Michelle Dunlop                                 Sean Brennan
------------------------------                  ------------------------------
Name of secretary (print)                       Name of director (print)

Shareholder Address:                  [STAMP]
                          ----------------------------------

                          ----------------------------------

                          ----------------------------------
Telephone Number:
                          ----------------------------------

Telecopy Number:
                          ----------------------------------

<PAGE>

                                                                     EXHIBIT A
<TABLE>
<CAPTION>
                                              Shares and Class to
Shareholder                                   be Sold Hereunder
-----------                                   -------------------
<S>                                           <C>

JTC Investment Management Pty, Ltd            1,864,991 Class C-1

Westpac Custodian Nominees Limited,
as nominee for NJI No. 1(A) Investment Fund   25,000 Class C-1
                                              333,333 Class C-3

Westpac Custodian Nominees Limited,
as nominee for NJI No. 1(B) Investment Fund   25,000 Class C-1
                                              333,333 Class C-3
</TABLE>

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