He snatched up the receiver and his free hand groped for the switch on the bedside lamp.
他一把抓起听筒，空着的手则摸索着找床头灯的开关。
《柯林斯英汉双解大词典》
2
You can take a cue from GCC: maintain many sets of environment variables per application and switch from one pool to another depending on the work at-hand.
At the bottom of the stairs my hand met an electric switch. I turned it, and a great electrolier of twelve red globes flooded the cellar with a red light.