Padre currently provides context sensitive help for Perl 5 and via the Perl6 plugin to Perl 6. The feature is extendable so it could be added to any type of file. It could be even added to things such as JQuery.
In order to activate the feature select some Perl 5 construct in a file that was recognized as Perl 5 and press F2. (Help -> Context Help)
See example in this blog http://ahmadzawawi.blogspot.com/2009/09/whats-new-in-padre-046.html
Or this screencast on youtube : http://www.youtube.com/watch?v=yGPLXNUbffY
- improve speed
- factor out the feature to Code::Explain to be usable by other editors and tools