If you want to output a properly parenthesized mathematical expression, you'll have to do so on the fly, examining the tree that I assume you have in your Arithmetic object. For example, if you have $x = ($a + $b) * $c;, then you probably have a tree like: 
Arithmetic::Multiply(
  Arithmetic::Add(
    Variable('a'),
    Variable('b')
  ),
  Variable('c')
)

[download]
When you're walking that tree, when you get to a Multiply or Divide node, you have to check to see if its children are Add or Subtract nodes; if they are, those child nodes need to be surrounded by parentheses when output.
Jeff japhy Pinyan, P.L., P.M., P.O.D, X.S.: Perl, regex, and perl hacker
How can we ever be the sold short or the cheated, we who for every service have long ago been overpaid? ~~ Meister Eckhart

In reply to Re: Using overload to parse arithmetic terms by japhy
in thread Using overload to parse arithmetic terms by esskar

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