There's a module named if which was written specifically to do what you want. It comes with Perl.

script.pl

use strict;
use warnings;

# Initialized in BEGIN so the use can see $VERSION.
use vars qw( $VERSION );
BEGIN { $VERSION = 0.1; }

#use if $VERSION < 1, 'bytes';
use if $VERSION < 1, 'Proof' => 'try1';
use if $VERSION > 1, 'Proof' => 'try2';
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Proof.pm

package Proof;

sub import { print('used at ', $_[1], $/); }

1;
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