Matching a regular expression within a string

Regular expressions provide us with a powerful method to locate an arbitrarily complex pattern within a string. The regexp command is similar to a Find function in a text editor. You search for a defined string for the character or the pattern of characters you are looking for and it returns a Boolean value that indicates success or failure and populates a list of optional variables with any matched strings. The -indices and -inline options must be used to modify the behavior, as indicated by this statement. But it doesn't stop there; by providing switches, you can control the behavior of regexp. The switches are as follows:

Switch	Behavior
-about	No actual matching is made. Instead regexp returns a list containing information about the regular expression where the first element is a subexpression count and the second is a list of property names describing various attributes about the expression.
-expanded	Allows the use of expanded...