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 $_;
}

    [download]
  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 $_;
}

    [download]
p.s. I was expecting this to work: 
foreach(() = @arr) {
   print;
}

[download]
but it doesn't loop even once. I think that's a bit weird, since 
$x = () = @arr;

[download]
actually sets $x to the size of the array.

In reply to Re: Is it safe to append to the array you are iterating over by bart
in thread Is it safe to append to the array you are iterating over by DrWhy

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