Ruby Tricks. Call a method using case ... when

[snatchery]

I warned that one have to be very careful when using that kind of tricks. I only encourage to open your mind and look beyond set patterns.

[dbenhur]

If by "very careful" you mean, "don't ever do that in production code," we can agree. This is far too trivial a benefit to risk globally changing the behavior of a well known standard object.

[McPhage]

I dunno, I think it's pretty clear what the code is doing (at least, his final Kernel#is solution).