I might have missed this somewhere in the documentation, but is Perl 6 going to have any documented notion of things like sequence points, undefined behaviour, etc? Is it going to mandate that function arguments are evaluated in any particular order (eg left to right)? Is it going to fix the behaviour if you modify a variable more than once in an expression?
Currently Perl 5 makes no written guarantees on many things, yet everyone has come to expect the current implementation's choices to be the way things must be. Is Perl 6 going to do the same, or will it be an explicit goal that anyone can implement a clean room Perl 6 compiler/runtime with only the written spec, without needing to match specific case behaviour encoded solely in regression tests? Perl 5 is also lets C's undefined behaviour poke through to the language level. Should Perl 6 avoid this completely? What's 1 << -1 in Perl 6? Nicholas Clark
