print "Please specify 2 filenames\n";
print "Filename 1:";
my $userfile1=<STDIN>;
chomp($userfile1);

print "Filename 2:";
my $userfile2=<STDIN>;
chomp($userfile2);

open OUT, ">CONCATENATED_FILES";
open (USER1, "<$userfile1") or die "Couldn't open file: $userfile1";
open (USER2, "<$userfile2") or die "Couldn't open file: $userfile2";
while(<USER1>)
{
	$line1=$_; 
	chomp $line1;
	print OUT $line1."\t";
	while(<USER2>)
	{
		$line2=$_; 
		chomp $line2;
		print OUT $line2."\n";
	}

}
close USER1;
close USER2;
close OUT;