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  1. PO
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    <p>I think this is somebody's gadget code. It doesn't look like the way you would want to write anything. But what it might illustrate best is that (in at least some versions) Perl is really running a more basic for loop, where:</p> <pre><code>for ( @l ) { #... } </code></pre> <p>Is replaced by: </p> <pre><code>for ( my $i = 0; $i &lt; @l; $i++ ) { local $_ = $l[$i]; #... } </code></pre> <p>Thus, because <code>@l</code> is <code>( 'c' )</code> when we've gone through twice, our trips through is already greater than <code>scalar( @l )</code>, so we're out. I've tested it out in a number of cases, and they seem to be equivalent. </p> <p>Below is the code I wrote to test cases. From it we can see that because of the shift, as soon as we're halfway through, the loop will exit. </p> <pre><code>use strict; use warnings; use English qw&lt;$LIST_SEPARATOR&gt;; use Test::More 'no_plan'; sub test_loops_without_shifts { my @l = @_; my @tests; for ( @l ) { push @tests, $_; } my @l2 = @_; my $n = @tests; my $i = 0; for ( $i = 0; $i &lt; @l2; $i++ ) { local $_ = $l2[$i]; my $x = shift @tests; my $g = $_; is( $g, $x, "expected: $x, got: $g" ); } is( $n, $i ); is_deeply( \@l, \@l2, do { local $LIST_SEPARATOR = .', '; "leftover: ( @l ) = ( @l2 )" } ); return $i; } sub test_loops { my @l = @_; my @tests; for ( @l ) { push @tests, shift @l; } my @l2 = @_; my $n = @tests; my $i = 0; for ( $i = 0; $i &lt; @l2; $i++ ) { local $_ = $l2[$i]; my $x = shift @tests; my $g = shift @l2; is( $g, $x, "expected: $x, got: $g" ); } is( $n, $i ); is_deeply( \@l, \@l2, do { local $LIST_SEPARATOR = ', 'c; "leftover: ( @l ) = ( @l2 )" } ); return $i; } is( test_loops( 'a'..'c' ), 2 ); is( test_loops( 'a'..'d' ), 2 ); is( test_loops( 'a'..'e' ), 3 ); is( test_loops( 'a'..'f' ), 3 ); is( test_loops( 'a'..'g' ), 4 ); is( test_loops_without_shifts( 'a'..'c' ), 3 ); is( test_loops_without_shifts( 'a'..'d' ), 4 ); is( test_loops_without_shifts( 'a'..'e' ), 5 ); is( test_loops_without_shifts( 'a'..'f' ), 6 ); is( test_loops_without_shifts( 'a'..'g' ), 7 ); </code></pre>
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    1. POWhy doesn't Perl's for() go through all of the elements in my array?
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    1. USAxeman
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    1. POWhy doesn't Perl's for() go through all of the elements in my array?
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    1. VO
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    1. COThis is /exactly/ the answer I was looking for. I decided to not push further and just accept the "don't do this" answers because there seemed to be some vague hostility going on, but what I really wanted to know is WHY you shouldn't do this. Thank you!
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      1. USJohn
 

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