sub what_next {
  my ($kernel, $job) = @_;
  my $next_step = shift @{ $job->{recipe} };
  if (defined $next_step) {
    $kernel->yield( $next_step => $job );
  }
  else {
    $kernel->yield( 'process_next_input' );
  }
}

##</code><code>##

sub process_next_input {
  ...;

  my $job = {
    input => $next_input,
    recipe => [ 'step_one', 'step_two' ],
  };

  what_next($_[KERNEL], $job);
}