I can't speak for what I was thinking at the time.

what.pl

if (!grep { $action eq $_ } @Controller::actions) {
    unshift(@parts, $action, 404);
    $action = 'error';
}

# …

my $sub;
{
    no strict 'refs';
    $sub = *{"Controller::$action"}{CODE};
}

#…

package Controller;
our @actions = do {
    no strict 'refs';
    grep { exists &{$_} && !/^_/ } keys %{__PACKAGE__.'::'};
};

sub error { … } # &c