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

# Hash that we'll store all the values (the name) in; keys are ports i
+n
# the form of ###/proto, i.e. 22/tcp
my %port2name;

open my $fh, '<', '/etc/services' or die "Failed open!  $!";

while (<$fh>) {
    next if /^#/ || /^$/;

    chomp;
    s/\s*#.*$//;
    
    my ($name, $port) = split /\s+/, $_;
    $port2name{$port} = $name;
}

close $fh;

# ... do whatever with the hash now
# For example, grab arguments from command line and
# print out name for each

for (@ARGV) {
    print exists $port2name{$_}
            ? "$_: $port2name{$_}"
            : 'Unknown port/proto combination.', "\n";
}
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