I'm pretty careful to keep personal stuff segregated from work stuff. That means that I generally don't install personal scripts at work (unless the personal stuff is publicly available as open source). That also means that if a company expects me to work at home, they'd better cough up equipment, because I'm not going to "taint" my personal equipment with their licensed software or intellectual property. I figure that keeping a strict separation is a good way to ward off problems. Am I going overboard? Perhaps. But I witnessed a couple of ugly incidents early in my career, and keeping a wall between job and personal work has just seemed like the safest, most ethical way to go.

The other benefit of leaving work stuff behind is that if I ever write the script again, the result is generally better. Rather than reusing something that I'd probably written in a hurry the first time, my subconscious has had a chance to watch out for new tricks and techniques that could be applied to a rewrite. Ever found yourself looking at a snippet and thinking "Oh wow, I wish I'd known that when I wrote XYZ!". By leaving work code at work, I'm giving myself the chance to take advantage of those insights.