Re: A few random questions from Learning Perl 3

[pg]

For the completeness of the "next" topic, we have to introduce the two brothers of "next": "last" and "redo".

1. next
   
   The "next" statement allows you to jump to the next iteration of the loop without executing the remaining statements of the current iteration.

   foreach (1..10) {
       next if ($_ == 9);
       print("$_  ");
   }
   

   Here's what it looks like:
   
   1 2 3 4 5 6 7 8 10
   
   As you can see, 9 is missing - this is because when the value of $_ hits 9, Perl uses the "next" statement to skip to the next iteration of the loop, and so 9 never gets printed.
   
   
2. last
   
   The "last" statement is used to exit the loop completely.

   foreach (1..10) {
       last if ($_ == 9);
       print("$_  ");
   }
   

   And here's the output:
   
   1 2 3 4 5 6 7 8
   
   
3. redo
   
   And finally, the redo statement lets you restart a particular iteration of the loop:

   foreach (1..10) {
       print("$_  ");
       if ($_ == 9 && $flag != 1) {
           $flag=1;
           redo;
       }
   }
   

   In this case, here's what you'll see:
   
   1 2 3 4 5 6 7 8 9 9 10

[talexb]

Excellent answer, with one small adjustment to the last example to do with redo ..

my $flag = 0;
foreach (1..10) {
    print("$_  ");
    if ($_ == 9 && $flag != 1) {
        $flag=1;
        redo;
    }
}

I have initialized flag to zero at the beginning of the loop. This was, of course, understood :) by all readers, but for the newcomer, it might be helpful.

--t. alex
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