use Parse::RecDescent;

$grammar = << 'STOP';
functiondefine:	/function/i name "(" parameter[ $item[2] ](s? /,/) ")" "{"

name:			/[A-Za-z][a-zA-Z0-9_]*/

parameter:		name /as/i variabletype
				{ warn $arg[0] }

variabletype:	/variant/i | /array/i | /keyarray/i
STOP

$parser = new Parse::RecDescent($grammar);


$text = << 'STOP';
function myfunction(something as variant, somethingelse as array, foo as keyarray) {

}
STOP

$parser->functiondefine($text);