Some folks like to use labeled blocks as an odd form of commenting. However, if you look at how Test::More implements SKIP blocks, you'll be rather horrified at the how it works :) (if the SKIP value is true, there's a last SKIP call).

sub skip {
    my($why, $how_many) = @_;
    my $tb = Test::More->builder;

    unless( defined $how_many ) {
        # $how_many can only be avoided when no_plan is in use.
        _carp "skip() needs to know \$how_many tests are in the block"
          unless $tb->has_plan eq 'no_plan';
        $how_many = 1;
    }

    for( 1..$how_many ) {
        $tb->skip($why);
    }

    local $^W = 0;
    last SKIP;
}
[download]

That relies on the SKIP label in the test, even though you don't see the last call.

Egads.

Although I haven't looked inside Test::More, I think I see what you're talking about. I tried this:

#!/usr/bin/perl

use warnings;
use strict;

sub tear_us_outta_here {
    print "Getting out of loop labeled FOO.\n";
    last FOO;
}

FOO: for ( 1 .. 10 ) {
    print "At $_.\n";
    if ( $_ == 4 ) { tear_us_outta_here(); }
}
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~~~ yields ~~~

At 1.
At 2.
At 3.
At 4.
Getting out of loop labeled FOO.
Exiting subroutine via last at ./foo.pl line 8.
[download]

That looks kinda' weird and scary to me... :)

Heh,.. for this sort of stuff, we should have a Halloween Perl-ghost-story-hour every October:

{dark room with flashlight shining up on an upright dead-tree printout of some code}:
"On this very line of code, many iterations ago, for no apparent reason, the loop... abruptly ended! Some say it was a hardware failure, others suggest deep magic at work in the bowels of the interpreter..."

;)

EDIT: Thanks for all the replies and interesting suggestions folks. Seems like, as Ovid suggests, the original author of the code I'm looking at just used the labels as some off form of odd commenting -- especially considering that there isn't any pod in the code.

Checker:
{
  my %seen;

  sub Checker
  {
    my $value = shift;
    if (defined($seen{$value}))
    {
      return $value;
    }
    else
    {
      $seen{$value} = 1;
      return;
    }
  }
}
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my $age;
INPUT: {
    print "Please enter your age: ";
    $age = <STDIN>;
    if ( $age !~ /\D/ ) {
        last INPUT;
    }
    redo INPUT;
}
[download]

Is there any specific advantage to the label there?

That appears to work just as well with none (except you need a chomp).

I'm not much taken with "if $age does not contain a non-digit, were done". How about:

my $age;
{
    print "Please enter your age: ";
    chomp( $age = <STDIN> );
    redo if $age =~ /\D/;
}

Please enter your age:
Mind your own
Please enter your age:
As old as m'tongue and a little older than m'teeth.
Please enter your age:
300000000000
[download]

---

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

Lingua non convalesco, consenesco et abolesco. -- Rule 1 has a caveat! -- Who broke the cabal?

"Science is about questioning the status quo. Questioning authority".

In the absence of evidence, opinion is indistinguishable from prejudice.

The only real benefit is reader clarity. By labelling it, you're giving a reason for a bare-block.

Also, my personal style - I (mostly) always put a label with every last and redo. (I don't for next because next is much more common.)

---

My criteria for good software:

1. Does it work?
2. Can someone else come in, make a change, and be reasonably certain no bugs were introduced?

They can be used as a target for the goto function:

abc: { sleep 1; print "japh\n"; }
goto abc;
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SWITCH: {
   if (...) { ..... ; last SWITCH }
   elsif (...) { ..... ; last SWITCH }
   elsif (...) { ..... ; last SWITCH }
}
[download]

If you use elsif, what's the point of the last statements?

it's there for consistency's sake only because I am obsessed with it... :D you can leave it out, but if you want to add more elsif, you have to remember to put 'last SWITCH' on that block... saving me from future bugs :D

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badaiaqrandista