Hi kcott, thanks for your answer :).

I also tried inlining the results (now discarded, but it was something like: "sub hrkeys () { keys %$hash_ref }"): that proved to be slower than using "@keys".
The () prototype makes a function a candidate for inlining, but only if the function doesn't have side effects and returns a constant value. keys can both have side effects (when working on a tied hash), and isn't guaranteed to return a constant value so your function couldn't be inlined.

I didn't think of caching. That's a good idea, and might put "sum(0) map" back in the picture; however, as you stated, that will depend on the OP's data (which hasn't been shown).
Well I used your code to try, and the runtime is divided by ten. But that's because all the keys in the outer hash are identical, so the the sum is only computed once, and the cache is used everytime after that. I doubt the OP's data is that redundant :). Here's my code BTW: 
sub eilys_code {
    my $bar;
    my %cache;
    my @keys = keys %$hash_ref;

    for my $outer (@$array_ref) {
        my $sum;
        for my $inner (split /-/, $outer) {
          $sum = $cache{$inner} //= sum map { $_->{value} } @{ $foo->{
+$inner} }{@keys};
        }
        push @{$bar->{$sum}}, $outer;
    }

    print '*** kens_code ***';
    print "@{[ $_, $#{$bar->{$_}}, $bar->{$_}[0] ]}" for keys %$bar;
}

[download]

The fact that with this sample data all the sums are identical makes this test less representative though, because push @{$bar->{$sum}}, $outer; autovivifies an array only once.

I'm not completely averse to single-letter variable names, such as $i for a loop index
I think $x, $y and $z as coordinates are fine. I still try to avoid $i though, because most of the time you don't need a loop index in perl, so if one is needed, there's probably a meaningful name to explain why.

In reply to Re^3: Optimize a perl block by Eily
in thread Optimize a perl block by IruP

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.