[disclaimer: I'm the author of CGI::Compress::Gzip, which provides similar functionality]
This module auto-detects if the client browser supports Gzip compression and, if so and if appropriate, compresses STDOUT. Similar functionality is provided by:
This module might have earned a "4" overall, but it does not have any tests and (less significantly) the documentation does not include a discussion of similar modules. I know from personal experience that the tests are the hard part of this functionality.
Unlike CGI::Compress::Gzip, this module is not a subclass of CGI. That is either a good thing or a bad thing, depending on whether you're after ease of use or speed. This module is much lighter weight than CGI::Compress::Gzip.
My brief perusal of this code suggests that under mod_perl, the programmer might need to explicitly close STDOUT for it to work, but I'm not positive.