[omouse]

The important thing is to learn the concepts and structures that programming languages indirectly talk about.

If you understand the differences between the OO concepts in Java, Ruby and Python, then you'll find it easy enough to pick up the surface layer (the syntax) of the languages.

[gaius]

This is true but a large part of "knowing" a language is knowing its standard library, where to find the function you need, and which of several similar functions is the exact one you want. The syntax you can learn in a day, but the libraries need time.