Advent 2013 day 09 - final example

gistfile1.txt

my $lisp-list = 1 => 2 => 3 => Nil;  # it's nice that infix:<< => >> is right-associative                                            
Pair.^add_fallback(
    -> $, $name { $name ~~ /^c<[ad]>+r$/ },  # should we handle this? yes, if /^c<[ad]>+r$/                                          
    -> $, $name {                            # if it turned out to be our job, this is what we do                                    
        -> $p {
            $name ~~ /^c(<[ad]>*)(<[ad]>)r$/;        # split out last 'a' or 'd'                                                     
            my $r = $1 eq 'a' ?? $p.key !! $p.value; # choose key or value                                                           
            $0 ?? $r."c{$0}r"() !! $r;               # maybe recurse                                                                 
        }
    }
    );
is $lisp-list.caddr, 3, 'Pair.^add_fallback';