Could you elaborate on your design and explain what the acronym's mean?

Any:    A pointer to anything.
Refco:  Reference counter.
Fl:     Flags.
T:      Type.
PVX:    Pointer value (a pointer to a string).
CUR:    Length of above string.    
LEN:    Size of allocated area for string.
IVX:    Integer value.

For an SvIV, the PVX, CUR and LEN values are unused.

For much more details, visit Gisles PerlGuts Illustrated.

Abigail