in reply to Send x% of the users to A, the rest to B

This one-liner shows that if you use rand() < 0.5 to decide between locations -- even if the rand calls are in different invocations of perl -- the distribution will be fairly split:

perl -E"{++$t;$r=`perl -E\"say rand()\"`;$r<.5?++$a:++$b; printf qq[\r +%.3f : %.3f], $a*100/$t, $b*100/$t; redo}" 49.350 : 50.650

With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.

RIP Neil Armstrong