isc

#!/usr/bin/env perl 

use strict;
use warnings;

my $id1 = $ARGV[0] || "id1.txt";
my $id2 = $ARGV[1] || "id2.txt";

my %list1 = ();
my %list2 = ();

open (ID1, $id1) or die "$!\n";
while (<ID1>) {
	chomp;
	s/\s//g;
	if (/(\S+)/) {
		$list1{$1} = 1;
	}
}
close ID1;

open (ID2, $id2) or die "$!\n";
while (<ID2>) {
	chomp;
	my @w = split /\s/;
	$list2{$w[0]} = $_;
}
close ID2;

foreach my $id (sort keys %list1) {
	if (exists $list2{$id}) {
		print $list2{$id}, "\n";
	}
}