I am considering pursuing a position as a programmer in the future. I want to know what, if there is one, is the standard for someone to be considered proficient or fluent in a programming language. For instance I have read a few programming books and have written some programs, but I certainly feel like I have a long way to go before I could program at a professional level. There is always new stuff to learn, but at what point can someone say the "know" a language?