#!/usr/bin/perl -w $file1 = "list1"; $file2 = "list2"; open (FIRST,"<$file1") || die "cannot open list1\n"; open (SECOND, "<$file2") || die "cannot open list1\n"; while ($line = <FIRST>) { chomp $line; $hash{ $line } = 1; } close FIRST; while ($newLine = <SECOND>) { chomp $newLine; if (exists $hash{ $newLine }) { print "$newLine\n"; } } close SECOND;