Regular expressions are used for powerful pattern-matching of substrings within strings. They can be used to search for a substring in a string, based on patterns—and then to extract or replace the matches. Julia provides support for Perl-compatible regular expressions.
The most common way to input regular expressions is by using the so-called nonstandard string literals. These look like regular double-quoted strings, but carry a special prefix. In the case of regular expressions, this prefix is "r". The prefix provides for a different behavior, compared to a normal string literal.
For example, in order to define a regular string that matches all the letters, we can use r"[a-zA-Z]*".
Julia provides quite a few nonstandard ...