Many programs use regular expression to find & replace text. However, they tend to come with their own different flavor.
Tue 14 Apr 2015 08:12:50 PM CEST - permalink -
You can probably expect most modern software and programming languages to be using some variation of the Perl flavor, "PCRE"; however command-line tools (grep, less, ...) will often use the POSIX flavor (sometimes with an extended variant, e.g. egrep or sed -r). ViM also comes with its own syntax (a superset of what Vi accepts).
This cheatsheet lists the respective syntax of each flavor, and the software that uses it.