#!/usr/bin/env perl

use strict;
use warnings;
use autodie;

open my $fh1, '<', 'ABC';
while (defined(my $line1 = <$fh1>)) {
    chomp $line1;
    open my $fh2, '<', 'CDE';
    while (defined(my $line2 = <$fh2>)) {
        chomp $line2;
        print "line1 : $line1  line2 : $line2\n";
    } 
}