See the current Perl documentation for IO::File.
Here is our local, out-dated (pre-5.6) version:

IO::File - supply object methods for filehandles

use IO::File;
$fh = new IO::File;
if ($fh->open("< file")) {
print <$fh>;
$fh->close;
}
$fh = new IO::File "> file";
if (defined $fh) {

IO::File inherits from IO::Handle and IO::Seekable. It extends these classes with methods that are specific to file handles.
CONSTRUCTOR
IO::File. If it receives any parameters, they are passed to the method open; if the open fails, the object is destroyed. Otherwise, it is returned to
the caller.
IO::File opened for read/write on a newly created temporary file. On systems where
this is possible, the temporary file is anonymous (i.e. it is unlinked
after creation, but held open). If the temporary file cannot be created or
opened, the IO::File object is destroyed. Otherwise, it is returned to the caller.
If IO::File::open receives a Perl mode string (``>'', ``+<'', etc.) or a
POSIX
fopen() mode string (``w'', ``r+'', etc.), it uses the basic Perl
open operator.
If IO::File::open is given a numeric mode, it passes that mode and the optional permissions
value to the Perl sysopen operator. For convenience, IO::File::import tries to import the
O_XXX constants from the Fcntl module. If dynamic
loading is not available, this may fail, but the rest of IO::File will
still work.
perlfunc, perlop, Handle Seekable
Derived from FileHandle.pm by Graham Barr <bodg@tiuk.ti.com>.