use Template;

{
    package MyStash;
    use base qw(Template::Stash);

    sub undefined {
        my $self = shift;
        my @ident = shift;

        print "(".join("|",@ident).")\n";

        if (@ident > 1) {
            return '';
        } elsif ($ident[0] eq 'adjective') {
            return 'red';
        } elsif ($ident[0] eq 'noun') {
            return 'fox';
        } elsif ($ident[0] eq 'verb') {
            return 'jumped';
        } else {
            return '';
        }
    }
}

my $stash  = MyStash->new;
my $string = "The [% adjective %] [% noun %] [% verb %] over the river.\n";
Template->new(STASH => $stash)->process(\$string);