Correct, I'm referring to the magic added by sv_magic.
$ perl -MDevel::Peek -e'Dump( $1 )'
SV = PVMG(0x561e81adde40) at 0x561e81af86f0
REFCNT = 1
FLAGS = (GMG,SMG) # Has get magic, has set magic
IV = 0
NV = 0
PV = 0
MAGIC = 0x561e81b067d0 # Magic's data, incl callbacks
MG_VIRTUAL = &PL_vtbl_sv
MG_TYPE = PERL_MAGIC_sv(\0)
MG_OBJ = 0x561e81af86d8
MG_LEN = 1
Magic is used by most punctuation vars (e.g. $!, $$, %ENV, %SIG), tie, lvalue operators (specifically substr, vec, pos and $#a), f( $h{ x } ) (to prevent autovivification) and more.
