Yes, or you can iterate over a copy if you want to delete items:
multiset m=(<"Stone","2","%70">); foreach(m + (<>);string k;int one) { if(k=="%70") { m[k]=0; break; } }
multiset direct_add=m-(<>); werror("%O %O\n\n", (array)direct_add, direct_add);
Can be slower, but it's less code.