vim

Using tabs

:n and :prev navigate.

:args see which file are open.

:n test.pl to add a file.

Using windows

Ctrl-W s and Ctrl-W v to split the current window horizontally and vertically.

Ctrl-W w to swhitch between open windows, and Ctrl-W h (or j or k or l) to navigate through open windows.

Ctrl-W c to close the current window, and Ctrl-W o to close all windows except the current one.

:e file to add a file.

:ls see the current state of buffers.