A regular expression (regex, regexp) is a string that describes or matches a set of strings, according to certain syntax rules. Regular expressions are used as a powerful and convenient way to recognise patterns in text.
Using PCRE Workbench you can write a Perl-style regex, set the appropriate compilation and execution flags and then interactively test the compiled regex against a line of text.
Using regular expressions you can validate e-mail adresses, extract ZIP-codes from documents, search for complex patterns in files and much more.