Spec clean-up
    
    - BR: perl(Carp)
    - Don't need to remove empty directories from buildroot
    - Don't use macros for commands
    - Drop redundant %{?perl_default_filter}
    - Enhance %description
    - Reinstate EPEL-5 compatibility:
      - Define buildroot
      - Clean buildroot in %install and %clean
    - Use tabs