mg_type  MGVTBL              Type of magic
    -------  ------              ----------------------------
    \0       vtbl_sv             Special scalar variable
    A        vtbl_amagic         %OVERLOAD hash
    a        vtbl_amagicelem     %OVERLOAD hash element
    c        (none)              Holds overload table (AMT) on stash
    B        vtbl_bm             Boyer-Moore (fast string search)
    D        vtbl_regdata        Regex match position data (@+ and @- vars)
    d        vtbl_regdatum       Regex match position data element
    E        vtbl_env            %ENV hash
    e        vtbl_envelem        %ENV hash element
    f        vtbl_fm             Formline ('compiled' format)
    g        vtbl_mglob          m//g target / study()ed string
    I        vtbl_isa            @ISA array
    i        vtbl_isaelem        @ISA array element
    k        vtbl_nkeys          scalar(keys()) lvalue
    L        (none)              Debugger %_<filename 
    l        vtbl_dbline         Debugger %_<filename element
    o        vtbl_collxfrm       Locale transformation
    P        vtbl_pack           Tied array or hash
    p        vtbl_packelem       Tied array or hash element
    q        vtbl_packelem       Tied scalar or handle
    S        vtbl_sig            %SIG hash
    s        vtbl_sigelem        %SIG hash element
    t        vtbl_taint          Taintedness
    U        vtbl_uvar           Available for use by extensions
    v        vtbl_vec            vec() lvalue
    x        vtbl_substr         substr() lvalue
    y        vtbl_defelem        Shadow "foreach" iterator variable /
                                  smart parameter vivification
    *        vtbl_glob           GV (typeglob)
    #        vtbl_arylen         Array length ($#ary)
    .        vtbl_pos            pos() lvalue
    ~        (none)              Available for use by extensions