A modeline for URxvt.

* Usage

  Download and put it in your ~perl-lib~ (or change your ~perl-lib~ to
  contain it), add ~modeline~ to your ~perl-ext-common~, and set the
  ~URxvt.modeline.command~ setting to a shell-executable which produces
  a single line of output which will be shown in the last line of the
  terminal.