SV

Space Vehicle.

Short for "scalar value". But within the Perl interpreter every "referent" is treated as a member of a class derived from SV, in an object-oriented sort of way. Every "value" inside Perl is passed around as a C language SV* pointer. The SV "struct" knows its own "referent type", and the code is smart enough (we hope) not to try to call a "hash" function on a "subroutine".