Regexp to check for regexp

Question

Regular Expressions

Is there a regular expression that checks if a given string is a regular expression?

Answer 1

It is impossible, because to check the regular expression it is necessary to check the balance of bracket sequences, which are not described by regular grammars.

Answer 2

And for what? Wouldn't it be easier to take and try to compile this line as a regular expression?

Answer 3

Absolutely any string, even an empty one, is a regular expression.