class MAIN is
  -- we need to implement the substitution
  regex_subst(re:REGEXP, s, sb:STR):STR is
    from, to:INT;
    re.match(s, out from, out to);
    if from = -1 then return s; end;
    return s.head(from) + sb + s.tail(s.size - to);
  end;

  main is
    s ::= "I am a string";
    re ::= REGEXP::regexp("string$", true);
    if re.match(s) then
      #OUT + "'" + s + "'" + " ends with 'string'\n";
    end;
    if ~REGEXP::regexp("^You", false).match(s) then
      #OUT + "'" + s + "'" + " does not begin with 'You'\n";
    end;
    #OUT + regex_subst(re, s, "integer") + "\n";
    #OUT + regex_subst(REGEXP::regexp("am +a +st", true), s, "get the ") + "\n";
  end;
end;