I don't know how reliable this source is: Pseudo hashes will die, but it's not the first time i have heard this news:

Pseudo hashes (the strange things that appeared with
the compiler in in 5.005-or-so) will die. They're
depreciated in 5.8, and will be gone from 5.10, because
they slow down all hashes and all arrays (by about 15%,
Schwern calculates). The functionality which currently is 
implemented with pseudo-hashes (fields.pm) will remain, 
probably using the new restricted hashes.

jeffa

mmmmm ... restricted hashes