halyard
An offline, stand-alone regular expression tester.
...but why?
If you want to test regular expressions on any sensitive data you might not trust one of those ("popular"?) online RegEx testing tools. Halyard instead runs totally offline, is open-source, and meant to be used stand-alone (i.e. its not a plugin for a browser that you do not use).
How to build it?
Dependencies
Install the GTK+ and GObject Introspection developer packages:
$ apt-get install libgtk-3-dev libgirepository1.0-dev
With Cabal
Install Cabal and build it:
$ curl https://gitlab.haskell.org/haskell/ghcup/raw/master/bootstrap-haskell -sSf | sh
$ cabal v2-install hsc2hs
$ cabal v2-build
With Stack
You can also build halyard via Stack! Install Stack, initialize the project once, and build:
$ curl -sSL https://get.haskellstack.org/ | sh
$ stack init
$ stack build