regexp for boundary changed to match a boundary with = sign

Hello,

I changed the regexp for boundary to match the '=' sign into the boundary, . which is allowed according to rfc 1341 ( see http://www.w3.org/Protocols/rfc1341/7_2_Multipart.html for details about BNF).Initially, the regexp split on the last '=' find and can't retrieve the boundary. It seems weird to use the = sign into boundary but some software like SoapUI generated boundaries with this sign.

Example of SoapUi content-type header with boundary : Content-Type: 
multipart/form-data; boundary="----=_Part_10_4245465.1397723989380"

Regards.