#!usr/bin/perl

use strict;   # don't leave home without it
use warnings; # same here!

use 5.10.0;   # so you can use say()

my @ports = qw( 21 22 23 );

# make a hash from the array for easier lookup
my %ports = map { $_ => 1 } @ports;

# use a lexical variable for your filehandle
open my $SERVICES_FILE, '<', '/etc/services' or die $!;

# read one line at a time with while()
while ( my $line = <$SERVICES_FILE> ) {
    
    # deal with new-line character at end of line
    chomp( $line );
 
    # 'postfix if' simplifies syntax
    say "Match Found: $line" if $ports{ $line };
}

# good practice to close filehandle
close $SERVICES_FILE or die $!;

# good practice to tell Perl when the program's done
__END__