ds_redbutton.pl is a script written in perl with the Tk GUI extension to allow a local user to join or leave a dynamic observing session at any time. In order to work, this script requires that the perl Tk extension is installed. First try running the script. If you get an error message about perl not finding the Tk extension, you can install it in at least two different ways:

1. Log in to the PCFS as root and type:
   1. cpan (you may be asked some questions, the default answers are usually OK).
   2. install Tk
2. Or download and install the extension by hand. It can be obtained from CPAN