# Supports ranges in any number of bytes.

sub parse_ip_mask {
   my ($ip_mask) = @_;
   my @checks;
   foreach (split(/\./, $ip_mask)) {
      if (/\[(\d+)-(\d+)\]/) {
         push(@checks, [ 0+$1, 0+$2 ]);
      } else {
         push(@checks, [ 0+$_, 0+$_ ]);
      }
   }
   return \@checks;
}

sub ip_check {
   my ($ip, $checks) = @_;
   my @ip = split(/\./, $ip);
   my $i;
   for ($i=0; $i<4; $i++) {
      return undef if ($ip[$i] < $checks->[$i][0]);
      return undef if ($ip[$i] > $checks->[$i][1]);
   }
   return 1;
}

##</code><code>##

my $ip_mask = parse_ip_mask('131.202.1.[3-4]');

foreach (qw(
   131.202.1.2
   131.202.1.3
   131.202.1.4
   132.202.1.4
)) {
   print(ip_check($_, $ip_mask)
      ? "$_ matches.$/"
      : "$_ doesn't match.$/"
   );
}

__END__
output
======
131.202.1.2 doesn't match.
131.202.1.3 matches.
131.202.1.4 matches.
132.202.1.4 doesn't match.

##</code><code>##

my $ip_mask = parse_ip_mask('131.202.1.[3-4]');

foreach (
   'Connection established to 131.202.1.2',
   'Connection established to 131.202.1.3',
   'Connection established to 131.202.1.4',
   'Connection established to 132.202.1.4',
) {
   my ($ip) = /(\d+\.\d+\.\d+\.\d+)/;
   print("Found matching ip $ip.$/") if (ip_check($ip, $ip_mask));
}

__END__
output
======
Found matching ip 131.202.1.3.
Found matching ip 131.202.1.4.