Debugging
You can use trace().
In FlashDevelop you can add breakpoints by clicking on the left side of a linenumber in the editor and choose 'test project' (blue play-button in top bar).
For HTML-target, this is send to the console.log of your browser For Flash-target inside flashdevelop's output window.
Debug messages only appear in a debug build. More info: http://haxe.org/doc/cross/trace
For debug purposes it could be very useful to use debug conditional compilation tags.
Documentation guide for Flambe - Targeted to version 4.0+
Flambe is MIT licensed and available for free. Feel free to contribute!