# $entity = the name of the entity (already initialized)
# $text = the full DTD (already initialized)

# comment out the empty entity definition
# e.g., <!ENTITY % foo  "    "  >
# so far this section works fine, wrapping the empty entity definition in comment tags
if ( $text =~ /(<!ENTITY\s+%\s+$entity\s+\"\s+\"\s+>)/ ) {

    print "Commenting out empty entity '$entity'\n";
    my $entity_def  = $1;
    $text =~ s/$entity_def/<!--\n$entity_def\n-->/;
}

# here's the problem: I want to find
# <!ELEMENT bar (#PCDATA  %foo;)*  >
# and remove the "%foo;"

if ( $text =~ /(<!ELEMENT\s+(\S+)\s+\(.*?$entity.+?\).+?>)/ ) {

    my $element_def  = $1;
    my $element_name = $2;

    print "Found empty entity '$entity' in $element_name " .
              "content model: $element_def\n";

    my $new_element_def = $element_def;

    $new_element_def =~ s/\|?\s*%$entity;//;

    print "Looking for $element_def\n";

    # this NEVER PRINTS--WHY?
    print "Found it!\n" if $text =~ /$element_def/;
}