2017-10-07 Note added by Athanasius: This node was copied from StackExchange. See also Re: Extract specify values in file log using perl.

hello perlmonks. I would like to optimize the following code: 

 
foreach my $a (@{ $array_ref }) {
    my $i = 0;
    foreach my $b (split('-', $a)) {
        foreach my $c (keys %{ $hash_ref }) {
            $i += $foo->{$b}->{$c}->{'value'};
        }
    }
    push @{ $bar->{$i} }, $a;
}

[download]

This loop take lots of time (about 30s on my server) because array_ref contains few millions of entries, it is not a memory problem but only CPU.

The split function returns only five elements and hash_ref is small (10 keys).

What changes I can do to run it faster !

In reply to 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.