I had a working hack of LVALUE types, barely, that kind of did interesting things. Most importantly it did compile miniperl. However life is never easy, a certain excellent french perl hacker, yes Rafael you, had changed LVALUE types since I last looked at them to be used in tie magic. So when you are fetching a tied value today, you actually get a LVALUE type with a undocumented 't' type, but this LVALUE type still uses tie magic instead of lvalue magic.
Implementing a emulation layer for tie magic seems fairly hopeless to me since tie magic is the most advanced type of magic and also since I am going totally rip it out when I redo hashes and arrays.
Obviously, the solution is simple, just rearrange the schedule a bit and RIP out hashes and arrays and implement them using PMCs instead, and this is exactly what I am going to do. So instead of January release there will be a leap day release (end of February) with lvalues, arrays and hashes being implemented using PMCs. This will be followed by a end of april - middle of may release which will have all SV types converted to PMCs, this release should be tested out in the wild against CPAN modules. Fixes to this release should lead up to a conference season release where the PMC conversion is declared to be done. This will let us focus on the next step, opcode to bytecode conversion.