use IO qw(Handle File); # loads IO modules, here IO::Handle, IO::File use IO; # DEPRECATED
IO::Handle IO::Seekable IO::File IO::Pipe IO::Socket IO::Dir IO::Select IO::Poll
Some other IO modules don't belong to the perl core but can be loaded as well if they have been installed from CPAN. You can discover which ones exist by searching for ``^IO::'' on http://search.cpan.org.
use IO; # loads all the modules listed below
The loaded modules are IO::Handle, IO::Seekable, IO::File, IO::Pipe, IO::Socket, IO::Dir. You should instead explicitly import the IO modules you want.