in reply to Is for(@$array_ref) construct optimized? YES!

You're preaching to the converted. :) If you use -MO=Deparse, you'll see that the for(;;) gets compiled to a while with a continue block, the latter being where the massive performance difference weighs in. Considering that the for(@array) form eradicates fence post errors from the root, there's rarely any good reason to use for(;;) in Perl.

Update: I forgot. Depending on your version of B::Deparse you may need increase the exposition level with the -x switch in order to see what things really look like to Perl under the hood. 
$ perl -MO=Deparse,-x7 -e 'for($i=0;$i<=10;$i++){}'
$i = 0;
while ($i <= 10) {
    ();
}
continue {
    ++$i
}
-e syntax OK
$ perl -MB::Deparse -e' print "$B::Deparse::VERSION\n"'
0.6
$ perl -v

This is perl, v5.6.1 built for i386-linux

[...]

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Makeshifts last the longest.

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Re: Re: Is for(@$array_ref) construct optimized? YES!
by Weasel (Sexton) on Jun 16, 2002 at 19:53 UTC
    Sorry, I just checked a situation and can not confirm your sayings. Here is my log: 
    D:\Work\PerlScripts\utl>perl -MO=Deparse -we "$x=[];for(@$x){}"
$x = [];
foreach $_ (@$x) {
    ();
}
-e syntax OK

D:\Work\PerlScripts\utl>perl -MO=Deparse -we "$x=[];for(;;){}"
Name "main::x" used only once: possible typo at -e line 1.
$x = [];
for (;;) {
    ();
}
-e syntax OK

D:\Work\PerlScripts\utl>perl -MO=Deparse -we "$x=[];for($i=0;$i<=$#x;$
+i++){}"
$x = [];
for ($i = 0; $i <= $#x; ++$i) {
    ();
}
-e syntax OK

    [download]
    This is probably version-dependent (which perl version you use?) and with less probablilty $^O-dependent (what is $^O in your case?)

    I think we'll find common denominator soon.

    update: after I saw your update I understood more and now I think we found that commond denominator that I've just mentioned. Thanks.

[reply]
[d/l]
      On Linux with Perl5.6.0: 
      $ perl -MO=Deparse -we '$x=[];for($i=0;$i<=$#x;$i++){}'
$x = [];
$i = 0;
while ($i <= $#x) {
    ();
}
continue {
    ++$i
}
-e syntax OK
      Screamer is right - but thanks for preaching anyway, not all of us are 'converted' just yet. ;)

      jeffa

      L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)
[reply]
        Aha! we see a difference between 5.6.0 and 5.6.1 with respect to this: 
        D:\Perl56\bin>perl -MO=Deparse -we "$x=[];for($i=0;$i<=$#x;$i++){}"
$x = [];
$i = 0;
while ($i <= $#x) {
    ();
}
continue {
    ++$i
}
-e syntax OK

D:\>perl -MO=Deparse -we "$x=[];for($i=0;$i<=$#x;$i++){}"
$x = [];
for ($i = 0; $i <= $#x; ++$i) {
    ();
}
-e syntax OK

        [download]
        Here I tried to compare 5.6.0 (I called it from 5.6.0 dir which is d:\perl56\bin in my computer) and 5.6.1 (it's in my $PATH)

        update I did update to call a snippet without compile errors; but explanation of results before and after update are same

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[d/l]

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