I am using ActiveState Perl 5.6 on a Windows 2003 Server, and am having some memory leak issues. Are there any good tools (or even bad tools which would give a clue) which
Since it's not been mentioned yet, Devel::Size will report the size of a data structure. There's no other information given and the rules it uses to determine the 'boundary' of your data structure are opaque. For simple structures this isn't a problem.
Devel::SizeMe is a hobby project of mine that aims to resolve the problems of Devel::Size and enable visualization of the entire memory usage of a perl interpreter. See my blog for extra information, including links to screencasts and videos. One of my goals is to enable detection and visualization of leaks, but that's still a way off yet.
Updates:
In addition to the other comments, you may find my Perl Memory Use talk at LPW2013 useful. I'd recommend watching the screencast as it explains the slides and has some cute visuals and some Q&A at the end.
I'd also suggest looking at Paul Evans Devel::MAT module which I mention in the talk.