Darting Viper
When using a dorn-dergar, you can quickly attack both near and distant foes.
Prerequisite: Base attack bonus +4, proficiency with the dwarven dorn-dergar.
Benefit: You may change whether you’re using the dorn-dergar as a normal or reach weapon as a swift action.
Normal: Changing whether a dorn-dergar is a normal or reach weapon is a move action.
Source: Dwarves of Golarion, p. 21