Perl looks for libraries in a series of locations, as described e.g. in perldoc perlrun.

Most commonly, this environment variable is set up in a user-specific or system-wide .profile file, or a Windows setting.   It can also be specified by use lib

Strictly speaking, Perl builds entries in an array named @INC, and it cycles through that array from beginning to end.   (The various methods I described are simply standard ways to populate that list.   The initial default entries in the list are hard-coded when the perl.exe executable is compiled.)

I’m afraid that I can make no useful comment concerning PerlApp...   I have not yet used that utility.   I don’t know how it assimilates the modules into the program that it produces, nor what runtime characteristics that (generated) program might subsequently have.