* Returns the matching close pair symbol for the given opening symbol.
* Currently returns a-z for A-Z, or )]}> for ([{<, or the input symbol if it
* is not a valid opening symbol.
* Returns the matching close pair symbol for the given opening symbol.
* Currently returns a-z for A-Z, or )]}> for ([{<, or the input symbol if it
* is not a valid opening symbol.