ometa InfixToPrefixParser {
  value    = (letter | digit)+:v -> v.join(''),
  addExpr  = addExpr:a ('+'|'-'):o mulExpr:m -> ['(', o, a, m, ')'].join(' ')
           | mulExpr,
  mulExpr  = mulExpr:m ('*'|'/'):o primExpr:p -> ['(', o, m, p, ')'].join(' ')
           | primExpr,
  primExpr = '(' expr:e ')' -> e
           | value,
  expr     = addExpr
}

tree = InfixToPrefixParser.matchAll('(1+2a2)*(b/3)', 'expr')