At least on 5.6.0 and later, Tie::RefHash seems to be in the standard distribution.

But you can use the stringized version of the handle as an index pretty easily. Since IO::Select->select returns your original handles, you end up with a hash index that looks like 'IO::Socket::INET=GLOB(0x83cfae0)'. That's perfectly usable, no?

You could also use the IO::Select::handles method to find the index of the handle of interest (returned by select). Or you could use the fileno of the handles as your hash key. Lots of ways to do it (this is Perl, after all...)