perl6 brainf*ck program

gistfile1.pl

use v6;

grammar Brainfuck::Grammar {
    rule TOP {^ [<cmd> || .+? ]* $}
    proto token cmd { <...> }
    token cmd:sym<ptr-inc>  {\>}
    token cmd:sym<ptr-dec>  {\<}
    token cmd:sym<inc>      {\+}
    token cmd:sym<dec>      {\-}
    token cmd:sym<input>    {\,}
    token cmd:sym<output>   {\.}
    token cmd:sym<loop>     {\[}
    token cmd:sym<end-loop> {\]}
}

class Brainfuck::Actions { ['sub offset($i) {$i > 0  ??  2 * $i  !!  - (2 *$i) + 1};',
                            'my @mem',
                            'my $ptr = 0;',
                            'my $idx = 0;',
                            $<cmd>>>.ast ]; }
    method cmd:sym<ptr-inc>($/)  {make '$idx = offset(++$ptr);'}
    method cmd:sym<ptr-dec>($/)  {make '$idx = offset(--$ptr);'}
    method cmd:sym<inc>($/)      {make '++@mem[$idx];'}
    method cmd:sym<dec>($/)      {make '--@mem[$idx];'}
    method cmd:sym<input>($/)    {make '@mem[$idx] = $*IN.getc.ord;'}
    method cmd:sym<output>($/)   {make '$*OUT.print( @mem[$idx].chr );'}
    method cmd:sym<loop>($/)     {make 'while @mem[$idx] {'}
    method cmd:sym<end-loop>($/) {make '}'}
}

Brainfuck::Grammar.parse($*IN.slurp, :actions(Brainfuck::Actions.new));
EVAL $/.ast.join("\n");