sS gazelle_purposeFromComments(LS comments) {
  new Matches m;
  for (S s : unnull(comments)) {
    if (swic_trim(s, "purpose:", m))
      ret m.rest();
  }
  ret "";
}

sS gazelle_purposeFromComments(S comments) {
  ret gazelle_purposeFromComments(tlft(comments));
}