Example AST transform (PIR-based)

transform while (Perl6::Grammar::statement_control) {
    .local pmc exprnode, exprpast
    .local pmc blocknode, blockpast
    ##  get AST for <expression>
    exprnode = node['expression']
    exprpast = tree.'get'('past', exprnode, 
                          'Perl6::Grammar::expression')
    ##  get AST for <block>
    blocknode = node['block']
    blockpast = tree.'get'('past', blocknode, 
                           'Perl6::Grammar::block')
    ##  build while loop
    .local pmc past
    past = new 'PAST::Op'
    past.'init'(exprpast, blockpast, 
                'node'=>node, 'pasttype'=>'while')
    .return (past)
}