use warnings;
use strict;

my $pat_file = 'pat.txt';
my $file = 'in.txt';

open my $pat_fh, '<', $pat_file or die $!;
my @patterns = <$pat_fh>;
chomp @patterns;
close $pat_fh;

open my $fh, '<', $file or die $!;

my @exists;

while (my $line = <$fh>){
    my ($ret) = grep { $line =~ /$_/ } @patterns;
    push @exists, $ret if $ret;
}

print "$_\n" for @exists;