/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>

##</code><code>##

/tmp/perlmonks>perl -MMod -e Mod::where
Script is in /tmp/perlmonks
Script basename is -e
Real script directory is /tmp/perlmonks
Real script basename is -e
Module was loaded from Mod.pm

/tmp/perlmonks>

##</code><code>##

/tmp/perlmonks>perl run.pl x
Cannot find current script 'run.pl' at /usr/share/perl5/FindBin.pm line 166.
BEGIN failed--compilation aborted at /usr/share/perl5/FindBin.pm line 166.
Compilation failed in require at /tmp/perlmonks/Mod.pm line 6.
BEGIN failed--compilation aborted at /tmp/perlmonks/Mod.pm line 6.
Compilation failed in require at run.pl line 11.
/tmp/perlmonks>

##</code><code>##

/tmp/perlmonks>touch /tmp/unrelated/run.pl

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

/tmp/perlmonks>

##</code><code>##

/tmp/perlmonks>perl -MFindBin run.pl x
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>