svoid dm_gazelle_newRuleDialog_2(S in) {
  dm_gazelle_newRuleDialog_2(in, dropPrefixTrim("+", lastLine(in)));
}

svoid dm_gazelle_newRuleDialog_2(S in, S out) {
  inputMultiLineText("New Gazelle Rule",
    in + "\n=> " + out,
    voidfunc(S s) {
      Pair<S, Bool> p = dm_gazelle_addRule(s);
      infoBox(p.b ? "Rule " + p.a + " added" : "Rule already there: " + p.a);
    });
}

Began life as a copy of #1021467