my @chains = qw(INPUT OUTPUT FORWARD);
my @rules = open_file($rules);

foreach (@chains) {
    for my $rule (@rules) {
        print $rule if ( $_ eq $rule );
    }
}


##</code><code>##

my FILE>>
INPUT
-p tcp -s 10.0.12.1 -j ACCEPT
FORWARD
-p udp -d 10.0.12.4 -j ACCEPT
OUTPUT
-p tcp -s 10.0..12.5 -j ACCEPT
FILE

my @chains = qw(INPUT OUTPUT FORWARD);

I Loop the array open then file and try to match first array item push on to new array until then next array item match.