Here are several use-cases this command would support:

script.rb:
    goto('http://www.google.com')
    text_field(:name, 'q').set 'ruby'
    button(:name, 'btnG').click

Execute it with:
 > watir script.rb

Or rename at script.wtr, and create a file association:

> script.wtr

Scripts can also be specified on the command line:

> watir -e "goto('http://www.google.com'); text_field(:name, 'q').set 'ruby'; button(:name, 'btnG').click"

Support -b switch to run invisibly


Automatic Browser Close

Consider adding an option to automatically close a script (no matter what) at the end.
* Need to do this automatically anyway if the window is not visible.
* But never auto close if we attached