You need something external to the loop to keep the state.

You could use a combination of the address of the calling opcode as a key to get the appropriate state, but you'd have no way to reset to the counter if you did that, so you wouldn't be able to last/return/die from within the loop.

Just look at each for example. To properly use each, you need to do:

keys %hash;  # Reset iterator
while (my ($k, $v) = each(%hash)) { ... }
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And even then, it doesn't nest because the iterator is per-hash, not per-each.

Did you have a look at the code I linked to? It keeps the state, by using the ref of the iterator-variable as key:

 use strict;
use warnings;
 
{ my %lists;
 
  sub deal {
    my $aref=shift;
    my $id= \$_[0];
    #print $aref,$id;
    $lists{$id}=$aref if (! exists $lists{$id} );
    if (@{$lists{$id}}){
      for(@_) {
    $_=shift @{$lists{$id}};
      }
      return 1; 
    } else {
      delete $lists{$id};
      return 0;
    }
  }
}
 
$\="\n";
 
#--------- here we go 
while (deal [1..9] => my ($a,$b,$c) ){
  print $a,$b,$c;
  while (deal [a=>1,b=>2] => my ($a,$b) ){
    print $a,$b;
  }
}
#--------- 
print "EXIT";
 
__DATA__ 
123
a1
b2
456
a1
b2
789
a1
b2
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But I have to admit that till now I haven't thought about last, that's indeed a problem...

Cheers Rolf

• You assumed that the iterator variable will be created at the same memory address every pass of the loop. It's a bad assumption. For example, the following code is an infinite loop:

  my @x;
  while (deal [1..9] => my ($a,$b,$c) ){
    print $a,$b,$c;
    push @x, \$a;
  }
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  Well, maybe not infinite, since deal is leaking memory every pass of the loop...

• You assumed that the loop will receive a new iterator each time. It's a bad assumption. For example, deal starts at the wrong number the second and third pass of the outer loop in the following code:

  for (1..3) {
    while (deal [1..9] => my ($a,$b,$c) ){
      print $a,$b,$c;
      last;
    }
  }
  [download]

Just like you need to call keys before each, you'd need to reset the iterator before entering the loop. You'd need

init_deal my ($a,$b,$c)
while (deal [1..9] => ($a,$b,$c) ){
   ...
}
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