#!/usr/bin/perl

#use strict;
use warnings;

my @list = qw(a b c);
foreach my $f(@list){
        foreach my $s(@list){
                my $aaa = $f.$s;
                open($aaa, ">", "test_$aaa.txt") or die;
        }
}

while(<DATA>){
        chomp;
        my $sub = substr($_, 0,2);
        print $sub "$sub\n";
}

__DATA__
aaK
acK
bcK
baK
bbK