The C Module defines an abstract base class that can be
used to build modules that capture output being sent on a filehandle
such as STDOUT or STDERR.

Several modules that come with the distribution do just that.
I.e., Capture STDOUT and STDERR. Also see James Keenan's
C on CPAN.

See L for a
discussion of these modules and examples of how to build a module to
sub-class from C yourself. If after reading the overview,
you would like to build a class from C, look here for
details on the internals.