For general information on Perls internal memory structures, I would look at illguts. The names for the various structures are best treated as Just Names, but the following mnemonics work for me:

SV - Scalar Value
IV - Integer Value
NV - Numerical Value
RV - Reference Value
PV - Pointer Value (like *char, for example)
LV - I haven't encountered this one, maybe it lives in illguts
GV - glob value. The glob is (I think) shorthand for global
AV - Array Value
HV - Hash Value
CV - Code Value (think subroutine reference)
FM - Format
IO - Filehandle
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The ops are also documented in illguts I believe.

Update: Typoo