Having no experience working with the nuts and bolts of Perl, all advice I can give you is a classic you probably have thought of as well. If the program segfaults, you should have a core file. Running this corefile through a debugger should get you some information, such as where you are getting your segfault (i.e. in which function), what the call stack leading to that function was, and the values of (C level) variables at that point. It helps if your library is compiled with -g (to add debugging information), but even without this you should get some information.

Here's how to do some of this with gdb on Linux, YMMV for other debuggers:

$ gdb -c core /usr/local/bin/perl
[snip]
(gdb) set args my_test_script.pl
(gdb) run
...something about segfaulting
(gdb) where
... shows what function you were in
(gdb) bt
... shows a backtrace of the stack, showing the code path to this func
+tion
(gdb) print variable
... prints variable, amazingly (supposing it is in scope)
(gdb) print *0xdeadbeef
... prints memory address contents (best guess at what it contains)
[download]

It is my experience that this usually puts me well on the way of finding the exact bug: at the least it shows you where to look.

Good luck!

Update: added asterisk before Oxdeadbeef.

CU
Robartes-