PADTMP hash pessimisation was fixed with commit 38bb37b9aa18dbe6.

Remove it from the TODO list.
@INC order was improved in a series of commits ending with e37778c28ba4f703.

Belatedly remove it from the TODO list.
5.14.0 adds Perl_cv_set_call_checker(), but no guide to inlining XSUBs.

Being able to inline simple XSUBs was listed as a TODO. 5.14.0 now provides
functionality for a compile-time "fixup" function for an XSUB, added using
Perl_cv_set_call_checker(). This has API-level documentation, but there is
no guide or tutorial on how to exploit this API to actually implement an
XSUB which can inline.
Refine the todo entry for install.html

Update the description of what needs doing. The splitting code exists, but
it's sub-optimal and not re-usable. Correct the name of the Makefile target -
it's 'install.html' with a period, not 'installhtml'.
Remove "Remove duplication of test setup" from the todo list.

It's no longer obvious which files in t/ contain significant amounts of
setup code which is duplicated. Common cases of skip logic have already been
moved into t/test.pl. The suggestion of replacing $Is_Foo checks with %Is is
not a clear-cut win - each $Is_Foo eliminated is only a 1 line saving, at the
cost of another testing idiom the future maintenance programmer has to become
familiar with.

The related suggestion "Migrate t/ from custom TAP generation" remains
something to do. There are still various files in t/ which could use be
converted to use the comparison functions of t/test.pl reducing code size,
improving failure diagnostics and where this eliminates manual test counters,
increasing flexibility for adding tests in the logically correct location
within the file.
Update the todo entry for makedef.pl duplicating C conditional compilation.

makedef.pl has been refactored to read from embed.fnc directly, cutting out
the embed.pl middleman. Correct the header filename - it's "intrpvar.h",
not "interpvar.h".
Remove the "POD -> HTML conversion in the core still sucks" todo entry.

Thanks to GSoC 2011, Pod::HTML has been refactored to use Pod::Simple::XHTML.
Remove the reference to -fstack-protector, which is done.

Exploring the use of -D_FORTIFY_SOURCE=2 remains to be done.
5.12.0 and later permit -C on the #! line with similar rules to -T

Whilst this isn't as totally flexible as it might be, it's good enough to
remove the todo entry, which was added when -C was forbidden on the #! line.
However, making -C parsing on the #! more flexible probably requires
removing the "feature" that a C<#line 1> directive triggers re-processing
of #! directives.
Remove two specific smartmatch suggestions from the todo list.

As smartmatch is "subject to review" these are unlikely to be appropriate.
Minor tweaks to the todo.

5.14 is long past - 5.18.0 is now the future stable release to aim for.
Correct the title of one entry to 0*o*ddd.
Add a missing close parenthesis.
Switching entersub ops from "XS" to "Perl" and back likely won't help.

Switching OPs goes against the grain of immutable optrees under ithreads -
it could probably be made to work, but the amount of extra effort would be
non-trivial.

Secondly, cache misses are the overriding speed hit on modern CPUs.
The code switching proposed would add complexity but only be able to change
the number of branch instructions encountered, which come a distant second
to cache misses as a speed hit. The code switching would not change the data
lookups needed, and hence not the cache misses they cause.
Drop the iCOW plan from the todo.

Dave has detailed reasons why he doesn't think that this would work. So it's
a bad idea to suggest it as something people should work on.
Remove 2 microperl suggestions from the todo list.

The --regen option added to Porting/checkcfgvar.pl makes creating uconfig.sh
pretty much automatic.

Whilst maintaining Makefile.micro could be made more automatic by templating
it based on MANIFEST, the benefits are probably never going to pay back the
cost of doing it, as we add (or remove) C and header files so rarely.
It would only really make sense as part of a system that did the same for
Makefile.SH, vms/descrip_mms.template and the multitude of Win* Makefiles.
Remove "Properly Unicode safe tokeniser and pads" from the todo

Brian Fraser (during GSoC), Father Chrysostomos, Zefram and others have done
most of the tasks suggested in this todo, so remove it from consideration as
it's clearly stale. The only possible work outstanding is how toke.c behaves
when PL_rsfp is marked as returning UTF-8, and when source filters return
SVs with SvUTF8() true. So leave this in as a comment in the Pod so that it
does not get lost, pending proper investigation.
Remove (?{...}) closures in regexps from the todo list.

Dave has this substantially done, and is working on finishing it off.
In the todo list, note who is already working on various suggestions.
Remove outdated todo items, and update and clarify others.