#! /usr/bin/env perl

use warnings;
use strict;

sub getIncludes {
   my $indent = shift;
   my $return = '';
   foreach my $domain ( @_ ) {
      $return .= ' 'x$indent . "$domain\n";
      my @lines = `dig $domain TXT | grep spf`;
      chomp @lines;
      foreach my $entry ( @lines ) {
         while ( $entry =~ m/include:([_a-zA-Z0-9\-\.]+)/g ) {
            $return .= &getIncludes( $indent+3, $1 );
         } # while
      } # foreach
   } # foreach
   return $return;
} # sub

while ( my $domain = shift ) {
   print &getIncludes( 0, $domain );
}
1;