Finding unused perl code

[Noah]

I inherited a large perl project with many small perl files spread out
over different directories. The project is an admin tool with a cgi interface.
I suspect that many of the files are no longer being used. Some entire
directories may be obsolete.

Is there a way I can identify the unused code?
Basically I need to locate Perl files that are not used by
any other Perl file in a directory tree.

Yours,
Noah