As FROGGS pointed out on IRC (http://irclog.perlgeek.de/perl6/2014-10-07#i_9469198) the behaviour on Parrot is not exactly as last year. I did a fresh build and now I get the "Null PMC access" errors only when putting the declaration in an extra block. (That's what happening in my tests where I use 'lives_ok { sub postfix:<\\>($) {} }, "OK"')
So for Rakudo on newly built Parrot: > sub postfix:< p >($) {}; say "alive" alive > { sub postfix:< \p >($) {}; }; say "alive" Null PMC access in find_method('clone') $ perl6-p -e 'sub postfix:<\\>($) {}; say "alive"' alive $ perl6-p -e '{ sub postfix:<\\>($) {} }; say "alive"' Null PMC access in find_method('clone') in block <unit> at -e:1 $ perl6-p -e 'use Test; lives_ok { sub prefix:<\\>($) {} }, "OK"' not ok 1 - OK # Failed test 'OK' # at -e line 1 # Null PMC access in find_method('clone')