=>cat /tmp/sorttest
#!/usr/opt/perl5/bin/perl
use strict;
use warnings;
use Benchmark;
 
srand(42); # the answer
my $elements = 2000000;
my %hash;
 
for (1..$elements) {
    my ($key, $one, $two) = rand =~/(\d\.\d{2})(\d{2})(\d{4})/;
    $hash{$key} = [$one, $two];
}
 
sub packed_default {
    my @sorted_keys =
        map substr($_,1), 
        sort map {pack('C', $hash{$_}[0])."$_"} 
        keys %hash;
    return @sorted_keys;
}
 
sub BroweserUK {
    my @sorted_keys = sort{ $hash{$a}[0] <=> $hash{$b}[0] } keys %hash;
}
 
timethese(10, {
    'packed_default' => \&packed_default,
    'BroweserUK'     => \&BroweserUK,
});

__end__

Benchmark: timing 10 iterations of BroweserUK, packed_default...
BroweserUK: 0 wallclock secs 
(0.07 usr + 0.00 sys = 0.07 CPU) @ 142.86/s (n=10)
            (warning: too few iterations for a reliable count)

packed_default: 0 wallclock secs 
(0.04 usr + 0.00 sys = 0.04 CPU) @ 250.00/s (n=10)
            (warning: too few iterations for a reliable count)