static <A> S pnlToString_rtrim(S prefix, Iterable<A> l) {
  ret dropLast(pnlToString(prefix, l));
}

static <A> S pnlToString_rtrim(Iterable<A> l) {
  ret dropLast(pnlToString(l));
}

static <A> S pnlToString_rtrim(A[] l) {
  ret dropLast(pnlToString(l));
}

static <A, B> S pnlToString_rtrim(Map<A, B> map) {
  ret dropLast(pnlToString(map));
}

ifclass MultiMap
static <A, B> S pnlToString_rtrim(MultiMap<A, B> map) {
  ret dropLast(pnlToString(map));
}
endif

Began life as a copy of #1020445