Regular expressions are a powerful practical tool for string processing. But there are simple examples of useful string processing tasks (like, say, removing brackets from an expression (E) -> E when E might itself contain brackets) which cannot be represented by a convenient regular expression.
Is there a language of expressions that can be used to conveniently process patterns defined by a context-free grammar?
Most domain-specific languages for context-free grammars are some variant of Backus-Naur form (BNF). A number of popular programming languages have BNF modules, like python's pyparsing module. They are also a first-class entity in the Raku programming language (a variant/successor to Perl) - see Raku rules. More commonly, you can write BNF grammars for various parser generators and then consume the generated parsers from a language of your choice.
