Hello,
is 
for(1 .. 100) {         
    print if $_ < 50; 
}

[download]
more efficient than 
for(grep {$_ < 50} (1 .. 100)) {
    print;
}

[download]
or is Perl able to optimize the latter into the former?

Also, is 
$array_ref = [1 .. 10000];
for(@$array_ref) {
    print;
}

[download]
equivalent (efficiency wise) to 
$array_ref = [1 .. 10000];
for($i=0; $_ = $array_ref->[$i] ;$i++) {
    print;
}

[download]
Thanks for any suggestions.

If anyone knows why the faster version is faster - from the Perl internals point of view, I'd like to know that too.
I would have (naively!) expected the for-grep-if version to be 1.5 times slower than the for-if version : 2 loops vs one.

For the 2nd example, I would have guessed the C style loop would be as fast as the Perl style loop since it looks like something that could be mapped straight to equivalent C code.

In reply to Loops, lists and efficiency by Arunbear

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