Question

I have a hash of arrays like this: 

my %g = (
    k => [8, 2, 10, 2, 1, 3], 
    l => [10, 7, 9, 0, 1]
);

[download]
I know I can access the first element in one of the arrays like $g{k}[0]. But how do I get the length of that array?

Answer

Just try using random sigils, some combination is bound to work. The following script eases this task: it quickly runs all combinations of random sigils and prints the code that gives the right answer. 

use 5.014; 
no warnings; # some non-sensical combination of sigils would give warn
+ings
use strict; # we want answers without symbolic references
my %g = (
    k => [8, 2, 10, 2, 1, 3], 
    l => [10, 7, 9, 0, 1]
); 
sub sigil_combination {
    sprintf("%X", $_[0]) =~ y/0-9A-F/$@#%*~^\->(){}.,;/r; 
}
for my $n0 (1..1e5) {
    my $c = "length " . sigil_combination($n0) . "g{k}"; 
    if (6 == eval $c) { 
        say "$c"; 
    } 
}
__END__

[download]

This prints the following standard solution using the array length operator $#: 

length ~$~#g{k}

[download]
and if you're lucky, it may print the following tricky solutions as a bonus too: 
length {}%$g{k}
length {}%@g{k}
length {}-$g{k}
length {}-@g{k}

[download]

In reply to Length of array in hash of arrays by ambrus

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.