s/iter      BrowserUK packed_default        SortKey
BrowserUK        71.7             --           -66%           -79%
packed_default   24.5           193%             --           -38%
SortKey          15.2           372%            61%             --

##</code><code>##

use Memchmark qw(cmpthese);

...

cmpthese(BrowserUK => \&BrowserUK,
	 packed_default => \&packed_default,
	 SortKey => \&SortKey );
__end__

test: BrowserUK, memory used: 102006784 bytes
test: SortKey, memory used: 85598208 bytes
test: packed_default, memory used: 182788096 bytes