Dear Monks,

today I spent my day bughunting a little subroutine and although it seems unlikely to me, I am about to state, that this is a Perl bug:

sub analyze {
  my $htree = shift;
  my $rul   = shift;
  my $hist  = (split /\n/, $htree->data)[0];
  my $str   = (split /\|/, $hist)[0];
  my ($k, $v);

  $hist = "|$hist";

  while(($k,$v) = each %$rul) {
    my @out = @{&proccode($str,$v)};

    for my $h (@out) {
      if($hist !~ /\|$h\|/) {
    my $new = $htree->append("$h$hist\n$k");
    &analyze($new,$rul);
    # PROBLEM: the @out loop is iterated again
    # even a 'next' does not force it to increment/end
      }
    }
  }
}

[download]
the problem of this routine is, that it seems to repeat the iteration within the for(@out) loop when returning from the recursive call to itself.

Which of course results in an endless loop for some cases. Even if I try to force it with "next" after the recursive call, it seems to be ignored.

Even if @out contains only one element, this happens.

So what is happening here? If I comment out the recursion call, the for(@out) loop behaves as it should.

sidenote: I encountered already a bug in Perl 5.8.0 when doing goto jumps within a for-loop (variables became undefined) - this was gone in 5.8.6 - which is what I'm using now.

Update: The 5.8.0 bug is ilustrated here.

Update2: Thanks to Fletch, Splinky and tlm, and because I had nothing to loose, I tried a modified version without the each iterator. Although I still do not see why it should influence the for(@out) loop, NOW IT WORKS! Instead of copying the hash, I extracted the keys into their own list. 

...
  my @rules = keys %$rul;

  for my $k (@rules) {
    my @out = @{&proccode($str,$$rul{$k})};
...

[download]

Bye
 PetaMem     All Perl:   MT, NLP, NLU

In reply to Iterator Problem with recursion by PetaMem

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