Definition: A regular expression is a set of pattern matching rules encoded in a string according to certain syntax rules. Although the syntax is somewhat complex it is very powerful and allows much more useful pattern matching than say simple wildcards like ? and *.
Example of a Regular expression
[-a-z0-9]+(\.[-a-z0-9]+)*
Regular expressions originated in the Unix world and are a part of the Perl language. If a regular expression language is similar to Perl's regular expressions, it is called Perl Compliant Regular expression (PCRE for short). This is pretty much a standard. The .NET framework includes pattern matching classes, as does Java.
Glossary:
A B C D E F G H I J K L M N O P Q R S T U V W X Y ZAlso Known As: PCRE
Examples:
Regular Expressions can match complicated patterns.
