use strict;
use warnings;


open( my $fh, '<', "input.txt" ) or die "Cannot open input file: $!";
chomp ( my @input_data = <$fh> );
close($fh);

open( my $frh, '<', "reference.txt" ) or die "Cannot open reference file: $!";
chomp ( my @ref_data = <$frh> );
close ($frh);

my @output = map {
    my $value = $_;
    grep { $value eq $_ } @ref_data;
} @input_data;

open ( my $wh, '>', "output.txt" ) or die ( "Cannot open the output file. $!");

print {$wh} $_ for @output;
close($wh);