Another option is to use Module::ScanDeps::scandeps (see docs at https://metacpan.org/pod/Module::ScanDeps#scan_deps).

If I remember correctly, this will handle use lib calls so if you pass it all the .pl files in your copy of the client's environment then it should find all the dependencies and their locations without needing to execute the code.

You will need to parse the results, but that's perhaps a small price to pay.

It also will not handle mylib or rlib calls if they are used.