Regular Expressions Regular Expressions Concepts and Editorials Perl uses a concept known as Regular Expressions for its matching and substitution operator. Regular Expressions permeate the Unix world, and are common in everything from the terminal shell to the system libraries. Regular Expressions can get tremendously complex, but are tremendously powerfull. They are a power tool, and not for the faint of heart. The concepts behind Regular Expressions are quite simple, however, and can be simple to write, and can replace pages of convoluted code logic.
Regular Expressions can be very difficult to read, but are generally reasonably quick to rewrite.
They have been called write only code, and to some degree this is the case. The two main uses of Regular Expressions in Perl are matching and substitution.