#!/usr/bin/perl
use strict;
use warnings;

my $file1='file1.txt';
my $file2='file2.txt';

my %lines;

open(my $fh, '<', $file1) or die("ERROR open $file1 $!\n");
while(my $line=<$fh>)
{ $lines{$line}=1; }
close($fh);

open(my $fh, '<', $file2) or die("ERROR open $file2 $!\n");
while(my $line=<$fh>)
{ print "$line" if($lines{$line}); }
close($fh);