Since 5.10, Perl regular expressions can match anything that's matched by a context-free grammar - and then some (backreferences add even more power). Matching balanced parenthesis is easy in 5.10 and later: /^(\((?1)*\))$/.

In reply to Re^2: RFC: Perl regex to validate arithmetic expressions by JavaFan
in thread RFC: Perl regex to validate arithmetic expressions by Serge314

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