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All,
Intrepid asked in the CB for a piece of code that would satisfy the following requirements:

Identify values in a list with the minimum length
Identify the maximum string value in the resulting list
Identify a random value from the resulting list

These have been generalized a bit as hashref keys were involved, but I provided the following straightforward solution:

my @min_keys = sort { length($a) <=> length($b) || $a cmp $b } keys %$
+hashref;
my $min = length $min_keys[0];

for ( 1 .. $#min_keys ) {
    if ( length $min_keys[$_] != $min ) {
        splice @min_keys, $_;
        last;
    }
}
# maxstr & random
print join "\t", $min_keys[-1], $min_keys[ rand @min_keys ];
[download]

There was a follow on discussion about how this could be done efficiently. While some were interested in a general solution that may be incorporated into List::Util, I felt a variation of the watermark algorithm was all that was needed to satisfy all the requirements in a single pass:

my @list = qw(zero one two three four five six seven eight nine ten el
+even twelve);

my ($maxstr, $random) = find_shortest( @list );
print join "\t", $maxstr, $random;

sub find_shortest {
    my ($pos, $len, $maxstr, @min) = (0, undef, '', 0, undef);
    my %dispatch = (
        -1 => sub {
                  ($len, $pos) = (length($_), 0);
                  ($min[$pos], $maxstr) = ($_, $_);
              },
         0 => sub {
                  $min[++$pos] = $_;
                  $maxstr = $_ if $_ gt $maxstr;
              },
         1 => sub { return },
    );
    for ( @_ ) {
       if ( ! defined $len ) {
           $len = length();
           ($min[$pos], $maxstr) = ($_, $_);
           next;
       }
       $dispatch{ length($_) <=> $len }->();
    }
    return ($maxstr, (@min[0..$pos])[rand $pos]);
}
[download]

There are still ways to improve on it, but I thought it was neat and only required a minimal amount of extra effort. How could you improve (keeping the original 3 requirements in mind)?
Cheers - L~R

In reply to Efficiently finding values of an extremity by Limbic~Region

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