using Mac computers for few years, I got accustomed of using the Cmd key on the keyboard as a standard Ctrl key.
With Ubuntu 13.04 on my Macbook Pro 5,3 (2009), the Cmd is used for Unity controls, and Ctrl for applications shortcuts. Is there any way to switch the two keys? So that, as an example, close a tab in Firefox would be Cmd+W instead of Ctrl+W?