No, Perl does not use $PATH to find modules. It searches the directories in @INC, which are set up when you compiled Perl. You might have been modifying @INC by setting your PERL5LIB environment variable. You might also have put this module in a directory where user nobody doesn't have permission to see them. Or, it might work from command line because @INC includes your current working directory ("."), and the module you need happens to be there.

You might just want to print out the contents of @INC from command line and CGI and compare what's in them.