Specify a rule name in a lexical variable

gistfile1.txt

{
    my $m = m(@strings[1]);
    ok $m, "mathced @strings[1]";
    is $m<paragraph>.elems, 2;
}

#is($f->convert('* list'), "\\begin{itemize}\n\\item list\n\\end{itemize}");


sub m($str, $rule = 'TOP') {
    diag("rule: $rule");
    my $m = JIRA::Formater::Wiki::Grammar.parse($str, :rule<$rule>);
    return $m;
}

# this results in this:

# rule: TOP
Method '$rule' not found for invocant of class ''
  in 'Grammar::parse' at line 6150:CORE.setting
  in 'm' at line 40:t/wiki.t
  in main program body at line 25:t/wiki.t

#### Now if I write it out, like put :rule<TOP>, it works?