Further to Properties, metadata and Perl celebrities, I took simonm's advice and replaced the boolean fields with a single field of space-separated keywords.

Given the functions get_eye_shapes to get all shape names, and get_eye_properties to get a shape's property hash reference, I've written a new function to get all shapes that contain a list of keywords:

sub find_eye_shapes {
  my @key = map( [ split/\s+OR\s+/ ], @_);
  my @ret;
  for my $s (get_eye_shapes()) {
    my $p = get_eye_properties($s) or next;  # no properties
    exists($p->{keywords})         or next;  # no keywords property
    my %h; @h{ split(" ", $p->{keywords}) } = ();
    my $found = 1;
    for my $k (@key) {
      grep(exists($h{$_}), @$k) or $found = 0, last;
    }
    push(@ret, $s) if $found;
  }
  return @ret;
}
[download]

This function has an implicit AND between each of its parameters. Some examples:

# Get all shapes with keywords: face AND person AND perlhacker
my @faces = find_eye_shapes('face', 'person', 'perlhacker');

# Get all shapes with keywords: face AND (person OR animal)
my @faces = find_eye_shapes('face', 'person OR animal');
[download]

Suggestions for improvements, both to the interface and the code above are welcome.

• The above interface is simple and hopefully covers the common cases, but is not complete because it does not accept an arbitrary boolean expression with AND, OR, NOT, XOR operators and parens. Huffman encoding suggests you should make easy shortcuts for common cases. Oh all right, I'm too lazy/stupid to implement a complete version without first asking here. :-)
• Given that there is an existing get_eye_shapes function (taking no parameters), should I introduce a new name find_eye_shapes or overload the existing get_eye_shapes function with a version that takes a list of keywords?
• Suggestions for a better name than find_eye_shapes are welcome.
• I was pondering using "any" and "all" (stolen from Perl 6 junction names) in the names or parameters somehow.