procedure main(A)
    rules := loadRules(open(A[1],"r"))
    every write(line := !&input, " -> ",apply(rules, line))
end

record rule(pat, term, rep)

procedure loadRules(f)
    rules := []
    every !f ? if not ="#" then put(rules,
                    rule(1(trim(tab(find("->"))),move(2),tab(many(' \t'))),
                         (="."|&null), trim(tab(0))))
    return rules
end

procedure apply(rules, line)
    s := line
    repeat {
       s ?:= tab(find((r := !rules).pat)) || r.rep || (move(*r.pat),tab(0))
       if (s == line) | \r.term then return s else line := s
       }
end