Three ideas:

• Try kill('ABRT',$pid). Traditionally ABRT has caused core dumps, so maybe on Java you'll get a stack dump.
• Try kill('BREAK',$pid). Perl handles CTRL-BREAK in a $SIG{BREAK} handler, IIRC, so maybe you can send a break signal this way?
• Win32::Console claims to have code to send break signals, though I haven't tried it.

Good luck! Hopefully one of these will help!