in reply to Is it safe to append to the array you are iterating over

The question then is is this violation of the general prohibition safe or was I lucky
Now I am confused. What do you expect,
  1. Perl loops over the original array, whatever you do to the array in the meantime
  2. Perl loops over the modified array
Frankly, I have no idea what to expect, you can make a case for both behaviors. In such a case, I'd say: don't do it. What will happen in this case might change over time, possibly because someone decided to fix perl's "erratic behavior".

What I think is safe, is this:

  1. Loop over the original array: make a temporary copy.
    foreach(my @temp = @arr) { push @arr, 'd' if $_ eq 'a'; push @arr, 'e' if $_ eq 'b'; push @arr, 'f' if $_ eq 'c'; print $_; }
  2. if you want to loop over the modified array, use the loop index:
    for(my $i = 0; $i < @arr; $i++) { local $_ = $arr[$i]; push @arr, 'd' if $_ eq 'a'; push @arr, 'e' if $_ eq 'b'; push @arr, 'f' if $_ eq 'c'; print $_; }
p.s. I was expecting this to work:
foreach(() = @arr) { print; }
but it doesn't loop even once. I think that's a bit weird, since
$x = () = @arr;
actually sets $x to the size of the array.