#! /usr/bin/perl
use strict;
use warnings;
my $path = "./IN/";
my $string = 'ABC';
my @filesWithString;

opendir (my $directory, $path) or die $!;
while(readdir $directory) 
    {
        next if $_ =~ m/^\./;
        my $fileName = "$path" . "$_";
        open (my $checkForString, "<", "$fileName");
        while (<$checkForString>)
        	{
        		print STDERR "$_";
        		if ($_ =~ m/$string/)
        			{
        				push (@filesWithString, $fileName);
        			}
        	}
        close $checkForString;
     }
closedir $directory;

for (@filesWithString)
	{
		my $newName = "$_".'.ABC.txt';
		open (my $old, "<", $_);
		open (my $new, ">", $newName);
		while (<$old>)
			{
				print $new "$_";
			}
		close $old;
		close $new;
	}