In Perl, what is the difference between a .pm (Perl module) and .pl (Perl script) file?

Question

What is the Difference between .pm (Perl module) and .pl (Perl script) file?

Please also tell me why we return 1 from file. If

Answer 1

A .pl is a single script.

In .pm (Perl Module) you have functions that you can use from other Perl scripts:

A Perl module is a self-contained piece of Perl code that can be used by a Perl program or by other Perl modules. It is conceptually similar to a C link library, or a C++ class.