use strict;
use NetAddr::IP;

# Sample data
my @sources = qw(192.168.0.19/32 192.168.0.20/32
                 192.168.0.21/32 192.168.0.22/32
                 192.168.1.72/30 192.168.1.76/30
                 192.168.1.80/30 192.168.1.84/30);
my @dests   = qw(192.168.1.73 192.168.1.77 192.168.1.81
                 192.168.1.85 int1 int2 int3 int4);
my @types   = qw(static static static static direct direct
                 direct direct);

sub lookup {
  my ($ip_obj, @RIB) = @_;

  for(my $i = 0; $i < @RIB; $i++) {
    next if $ip_obj == $RIB[$i]->{dest}; # don't check self

    if ($ip_obj->within($RIB[$i]->{source})) {

      return $RIB[$i]->{dest} if $RIB[$i]->{type} eq 'direct'

      return lookup($RIB[$i]->{dest}, @RIB);
    }
  }
}

my @RIB; # routing table. AoH
my %FIB; # forwarding table. H

# Produce 'useful' data struct from data
for (my $i = 0; $i < @sources; $i++) {
  $RIB[$i]->{source} = new NetAddr::IP($sources[$i]);
  # Only create NetAddr::IP obj if not a 'direct' route
  $RIB[$i]->{dest}   =
    $types[$i] eq 'direct' ? $dests[$i] :
                             new NetAddr::IP($dests[$i]);
  $RIB[$i]->{type}   = $types[$i];
}

for (my $i = 0; $i < @RIB; $i++) {
  next if $RIB[$i]->{type} ne 'static'; # only interested in
                                        # static routes
  $FIB{$RIB[$i]->{source}->addr()} =
    lookup($RIB[$i]->{dest}, @RIB);
}

print map{ "$_ -> $FIB{$_}\n" } sort keys %FIB;