I've read through the most obvious places...

Have you also checked out Perlguts Illustrated? I don't thinks so, or you'd have seen this:

The first things to look at are the data structures that represent Perl data; scalars of various kinds, arrays and hashes. Internally Perl calls a scalar SV (scalar value), an array AV (array value) and a hash HV (hash value). In addition it uses IV for integer value, NV for numeric value (aka double), PV for a pointer value (aka string value (char*), but 'S' was already taken), and RV for reference value. The IVs are further guaranteed to be big enough to hold a void* pointer.

update Link updated (future proofed) to always point to the latest version, as per the follow-up. Thanks, anon! I knew about "dist", but not that it would work for this particular case.