You can find the full list in the source of the the pp_gelem function, in pp.c.

...
    switch (elem ? *elem : '\0')
    {
    case 'A':
        if (strEQ(elem, "ARRAY"))
            tmpRef = (SV*)GvAV(gv);
        break;
    case 'C':
        if (strEQ(elem, "CODE"))
            tmpRef = (SV*)GvCVu(gv);
        break;
    case 'F':
        if (strEQ(elem, "FILEHANDLE")) {
            /* finally deprecated in 5.8.0 */
            deprecate("*glob{FILEHANDLE}");
            tmpRef = (SV*)GvIOp(gv);
        }
        else
        if (strEQ(elem, "FORMAT"))
            tmpRef = (SV*)GvFORM(gv);
        break;
    case 'G':
        if (strEQ(elem, "GLOB"))
            tmpRef = (SV*)gv;
        break;
    case 'H':
        if (strEQ(elem, "HASH"))
            tmpRef = (SV*)GvHV(gv);
        break;
    case 'I':
        if (strEQ(elem, "IO"))
            tmpRef = (SV*)GvIOp(gv);
        break;
    case 'N':
        if (strEQ(elem, "NAME"))
            sv = newSVpvn(GvNAME(gv), GvNAMELEN(gv));
        break;
    case 'P':
        if (strEQ(elem, "PACKAGE"))
            sv = newSVpv(HvNAME(GvSTASH(gv)), 0);
        break;
    case 'S':
        if (strEQ(elem, "SCALAR"))
            tmpRef = GvSV(gv);
        break;
    }
...
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So, it seems that your list is complete.