in my tests it's relative to the CWD at start

Right, which is why abs_path((caller)[1]) should work in a lot of cases, but certainly not all, which is why I asked OP if perhaps they have one of those cases.

Of course, since FindBin tries to give a correct answer, it should be possible to simply steal its code, change it so it doesn't just work on $0, and then apply it to caller in a module's import - if someone hasn't done this already.

> Right, which is why abs_path((caller)[1]) should work in a lot of cases,

Please correct me, but how is this better than abs_path($0) ?

AFAIK is abs_path the problematic part, because the CWD might have changed after a chdir

I suppose that $0 is even better, since caller might only show an intermediate module instead of the root script (untested)

Cheers Rolf
_{(addicted to the 𐍀𐌴𐍂𐌻 Programming Language :)
Wikisyntax for the Monastery}

Please correct me, but how is this better than abs_path($0) ?

Because it answers the OP's question... "Is there a way to get a module to return the full system path of the script using the module?"

$ cat lib/Foo/Bar.pm 
package Foo::Bar;
use warnings;
use strict;
use Cwd qw/abs_path/;

sub foo {
    my $callerfile = (caller)[1];
    print "DEBUG: caller=<$callerfile> \$0=<$0>\n";
    return abs_path($callerfile);
}

1;

$ cat y.pl 
use warnings;
use strict;
use Foo::Bar;
print Foo::Bar::foo(), "\n";

$ cat x.pl 
use warnings;
use strict;
do './y.pl';

$ perl -Ilib x.pl 
DEBUG: caller=<./y.pl> $0=<x.pl>
/tmp/y.pl
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