Example: if_stmt (cont'd)

rule if_stmt { 'if' <expression> 'then' <statement> {*} }

...

method if_stmt($/) {
    my $past := PAST::Op.new( $($<expression>),
                              $($<statement>),
                              :pasttype('if') );
    make $past;
}

$<expression> is the parse tree for <expression> in the rule

$($<expression>) is its AST representation

(same for $<statement> and $($<statement>) )