The code you posted doesn't compile. Please post a compiling code snippet and also a sample of what you have in /etc/services. (See Write-up formatting tips.)

Here's a rewrite of your code with several comments so you can see what's different:

( Edit: as hippo points out below, it's not likely that your /etc/services file actually contains lines containing only port numbers. This example code does not address that issue, nor try to use regular expression matching; it's just an example of how to work through your two data sets. )

#!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__
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