Given the names of two image files as arguments, this script will create a third image with the two side by side:

#! perl -slw
use strict;
use GD;

my $im1 = GD::Image->new( $ARGV[ 0 ] ) or die;
my $im2 = GD::Image->new( $ARGV[ 1 ] ) or die;

my( $x1, $y1 ) = $im1->getBounds();
my( $x2, $y2 ) = $im2->getBounds();
my( $x3, $y3 ) = ( $x1 + $x2, $y1 > $y2 ? $y1 : $y2 );

my $im3 = GD::Image->new( $x3, $y3, 1 );
$im3->copy( $im1, 0, 0, 0, 0, $x1, $y1 );
$im3->copy( $im2, $x1, 0, 0, 0, $x2, $y2 );

open PNG, '>:raw', 'new.png' or die $!;
print PNG $im3->png;
close PNG;

system 'new.png';;
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