Nested subroutines

Subroutines can be nested. In other words, you may define a sub inside another sub. Let's see it in the next example, which lists the present tense forms of regular English verbs:

sub list_verb_forms($verb) {
    sub make_form($base, $pronoun) {
        my $form = $base;
        # Adds the 's' ending for he, she, and it.
        # The check uses a regular expression.
        # We cover regular expressions in Chapter 11, Regexes.
        $form ~= 's' if $pronoun ~~ /^ [ he | she | it ] $/;

        return "$pronoun $form";
    }

    my @pronouns = <I we you he she it they>;

    for @pronouns -> $pronoun {
        say make_form($verb, $pronoun);
    }
}

list_verb_forms('read');

The result of this program is exactly what we wanted, as you can see here:

I read
we read
you read
he reads
she reads
it reads
they...