# 5. Variables local to a subroutine prefixed by some 
#    consistent prefix such as 'this_' or 'local_'. This way 
#    there never will be any confusion as to whether a 
#    given variable sprang into life in the subroutine
#    of if it exists in the outside world and might possibly 
#    get clobbered locally.

For this reason, the outside world variables are usually marked. Besides, global variables are bad design, object variables are prefixed with $self in Perl, and constants are usually ALL_CAPS.

IMHO the variables inside subs should not be prefixed by anything - it's the globals that should.