/tmp/perlmonks>cat run.pl
#!/usr/bin/perl

use strict;
use warnings;
use lib '/tmp/perlmonks';

# Tons of work omitted ... ;-)

@ARGV and chdir '/tmp/unrelated';

require Mod;

Mod::where();

/tmp/perlmonks>cat Mod.pm
package Mod;

use v5.12; # for say
use strict;
use warnings;
use FindBin;

sub where
{
        say "Script is in $FindBin::Bin";
        say "Script basename is $FindBin::Script";
        say "Real script directory is $FindBin::RealBin";
        say "Real script basename is $FindBin::RealScript";
        say "Module was loaded from $INC{'Mod.pm'}";
}

1;

/tmp/perlmonks>perl run.pl
Script is in /tmp/perlmonks
Script basename is run.pl
Real script directory is /tmp/perlmonks
Real script basename is run.pl
Module was loaded from /tmp/perlmonks/Mod.pm

/tmp/perlmonks>