How to print lines that don't match? - perl

Question

The script I have written outputs all lines from the file 2 that starts with a number that is in the file 1.
Question
How do I output all the other lines that didn't matched?
#!/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;
my #res;
open(FILE, '<', "1") or die $!;
while (defined (my $line = <FILE>)) {
chomp $line;
push #res, $line;
}
close FILE;
open(FILE, '<', "2") or die $!;
while (defined (my $line = <FILE>)) {
chomp $line;
$line =~ m/(\d+)/;
if (defined $1) {
foreach my $a (#res) {
if ($a == $1) {
print $line . "\n";
}
}
}
}
close FILE;
File 1
155
156
157
158
159
160
File 2
150 a
151 f
152 r
153 a
154 a
155 a
156 a
157 f
158 f
159 f

Answer 1

Your answer is pretty close actually: it's enough to change this
foreach my $a (#res) {
if ($a == $1) {
print $line . "\n";
}
}
... to this ...
my $found;
foreach my $a (#res) {
if ($a eq $1) { # we compare strings, not numbers, even if these strings are 'numeric'
$found = 1;
print $line . "\n";
last; # no need to look further, we already found an item
}
}
print "Not matched: $line", "\n" unless $found;
Yet still there's something to talk about. ) See, as all these number strings in the first file are unique, it's much better to use a hash for storing them. The code will actually not change that much:
my %digits;
... # in the first file processing loop:
$digits{$line} = 1;
... # in the second file processing loop, instead of foreach:
if ($digits{$1}) {
print $line, "\n";
} else {
print "Not matched: $line", "\n";
}
But the point is that searching in hash is MUCH faster than looping through an array again and again. )

Answer 2

use strict;
use warnings;
my %res;
open(FILE, '<', "1") or die $!;
while (defined (my $line = <FILE>)) {
chomp $line;
$res{$line} = 1;
}
close FILE;
open(FILE, '<', "2") or die $!;
while (defined (my $line = <FILE>)) {
if ($line =~ m/(\d+)/) {
print $line if not $res{$1};
}
}
close FILE;