awesome, thanks. Looks like that backport may be only for ruby 2.0 (not 1.9), and is a compiled C extension.
It won't take many lines of pure ruby code to do it for ruby 1.9 too, although presumably not performing quite as well as a C version.
At any rate, this is definitely something I and people I know need to do all the time, although apparently most ruby devs never need to do it; but I'm glad it's finally made it into stdlib.
I've completed a pure-ruby polyfill that should work on 1.9 as well as 2.0, any ruby interpreter including jruby. (It does have some issues mentioned in the readme).
It won't take many lines of pure ruby code to do it for ruby 1.9 too, although presumably not performing quite as well as a C version.
At any rate, this is definitely something I and people I know need to do all the time, although apparently most ruby devs never need to do it; but I'm glad it's finally made it into stdlib.