use warnings;
use strict;

my %dict = 
(
  sentence     => [[qw/ noun_phrase verb_phrase /]],
  noun_phrase  => [[qw/ Article Noun /]],
  verb_phrase  => [[qw/ Verb noun_phrase /]],
  Article      => [qw/ the a /],
  Noun         => [qw/ man ball woman table/],
  Verb         => [qw/ hit took saw liked /]
);


sub rand_elt
{
	return $_[rand scalar @_];
}


sub listp
{
	return ref($_[0]) eq "ARRAY";
}


sub generate
{
	my $phrase = shift;
	
	if (listp $phrase)
	{
		return [map {@{generate($_)}} @{$phrase}];
	}
	elsif (exists $dict{$phrase})
	{
		return generate(rand_elt(@{$dict{$phrase}}));
	}
	else
	{
		return [$phrase];
	}
}

print join(' ', @{generate("sentence")}), "\n";