When looking at regular expressions in the context of their host language or tool, there are three broad issues to consider:
-
What metacharacters are supported, and their meaning. Often called the regex “flavor”.
-
How regular expressions “interface” with the language or tool, such as how to specify regular-expression operations, what operations are allowed, and what text they operate on.
-
How the regular-expression engine actually goes about applying a regular expression to some text. The method that the language or tool designer uses to implement the regular-expression engine has a strong influence on the results one might expect from any given regular expression.