[Tabasco]

I don't see any existing function that will do what you want.
With DBI installed you could query the tiems table, but that doesn't guarantee that the item actually exists in the shared memory block.

You could try this though:

questmgr.h (somewhere under public

bool IsValidItem(int32 itemid);

questmgr.cpp

bool QuestManager::IsValidItem(int32 itemid)
{
    return(database.GetItem(itemid));
}

perlparser.cpp

XS(XS__IsValidItem);
XS(XS__IsValidItem)
{
    dXSARGS;
    if (items != 1)
        Perl_croak(aTHX_ "Usage: IsValidItem(itemid)");

    int32       itemid = (int32)SvUV(ST(0));
    bool        RETVAL;
    dXSTARG;


    RETVAL = quest_manager.IsValidItem(itemid);
    XSprePUSH; PUSHu((IV)RETVAL);

    XSRETURN(1);
}

Then add to the boot_quest function in perlparser.cpp

newXS(strcpy(buf, "IsValidItem"), XS__IsValidItem, file);

I can test it fully in the morning, but for now I can at least tell you that it compiles.