Re: Perl 5.9.4 released

[greenFox]

re state variables, do I read it correctly that we would no longer have to write:

{
  my $stately;
  sub some_func {
     # use $stately here
  }
}

to get a variable which maintains it's state? Neat. Can any-one give us a glimpse of the internals and let us know how that is done? My random guess: turn off garbage collection for state variables?

[theorbtwo]

Kind of. When you say sub foo {my $bar}, perl doesn't actually allocate a new variable every time you execute foo. Instead, it just clears the value. When you say state $bar it doesn't do that either. (This gets into the variable/value split, which is generally not talked about much in perl5-land. Suffice it to say, I did mean to say "variable" and "value" when I did.)

[grinder]

The main motivation behind state variables in perl5 land was to get rid of the awful hack:

my $var if 0;

Which was a way of getting state variables, but worked on an undocumented side-effect of how lexical pads are implemented. And the code is neater than having to close a an external variable over a routine.

The main patch (although there were a few tweaks a couple of months later as kinks were ironed out), as landed in the repository, is quite small, all things considered.

Basically it's just a tweak on lexical variables.

Another nifty feature of 5.9.4 is that $_ can be made lexical.

[Limbic~Region]

greenFox,
See How will you use state declared variables in Perl6? and specifically this response from TimToady.