sub DefaultHashValue {
    my %h = @_;
    my %r = reverse %h;
    my @k = sort values %h;
    return $r{ $k[0] }
}
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Neat and short, I thought. But wait, what exactly does it do? We pick up the asciibetically first value and find the corresponding key. It took me some time to understand it (yes, I'm tough). Could this code be written in a more speaking way?

I'd probably write it differently:

sub sort_keys {
    my %h = @_;
    my @s = sort { $h{$a} cmp $h{$b} } keys %h;
    return $s[0]
}
[download]

Our dropdowns vary in size from 2 elements to several hundreds. For pure curiosity (there were no speed problems), I benchmarked the solutions (see below). Interestingly, for lists over 50 elements, the original solution was faster.

It wasn't so hard to come with a winner. It's still readable, too:

sub min {
    my %h = @_;
    my $min = (keys %h)[0];
    $h{$_} lt $h{$min} and $min = $_ for keys %h;
    return $min
}
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Which solution would you use and why? Or, would you use something else? Why? (I stayed with the original).

For the interested, the full testing and benchmarking code:

#!/usr/bin/perl
use warnings;
use strict;

use Test::More;
use Benchmark qw{ cmpthese };


sub orig {
    my %h = @_;
    my %r = reverse %h;
    return $r{ (sort values %h)[0] }
}


sub Sort {
    my %h = @_;
    return (sort { $h{$a} cmp $h{$b} } keys %h)[0]
}


sub min {
    my %h = @_;
    my $min = (keys %h)[0];
    $h{$_} lt $h{$min} and $min = $_ for keys %h;
    return $min
}


# TEST
for my $t (
           { a => 'A', b => 'B', c => 'C' },
           { abc => 'ABC', def => 'ABC' , xyz => 'XYZ' },
           { 1 .. 1_000},
           { map int rand 100, 1 .. 1_000 },
          ) {
    my $o = orig(%$t);
    is  Sort(%$t), $o, "onleline-$o";
    is  min(%$t),  $o, "min-$o";
}


done_testing();


# BENCHMARK
for my $size (10, 100, 1_000, 5E4, 1E6) {

    my %h = map int rand 100, 1 .. $size;

    cmpthese(0,
             { orig => sub { orig(%h) },
               sort => sub { Sort(%h) },
               min  => sub { min(%h)  },
             });
}
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