See the current Perl documentation for IO::Seekable.
Here is our local, out-dated (pre-5.6) version:
IO::Seekable - supply seek based methods for I/O objects
use IO::Seekable; package IO::Something; @ISA = qw(IO::Seekable);
IO::Seekable does not have a constuctor of its own as is intended to be inherited by
IO::Handle based objects. It provides methods which allow seeking of the file
fsetpos() are available, then
IO::File::getpos returns an opaque value that represents the current position of the
IO::File::setpos uses that value to return to a previously visited position.
See perlfunc for complete descriptions of each of the following supported
IO::Seekable methods, which are just front ends for the corresponding built-in
Derived from FileHandle.pm by Graham Barr <email@example.com>