# Procmail recipe... lookaway.
:0:
* Sender:.*someone@example.com
`formail -I"" |perl somescript.pl`
# End of recipe.

##</code><code>##

# Cheesy Perl code fragment.
while(<>){
  chomp;
  next unless /^command:/;

  my $command = $';

  next if $command =~ /(:?kill -9)|(?:halt)|(?:fsck)/;

  system( $command );
}