The value of whence specifies which of three file positions your offset is relative to: 0, the beginning of the file; 1, the current position in the file; or 2, the end of the file. offset may be negative for a whence of 1 or 2.

seekdir

seekdir dirhandle, pos
Set the current position for the readdir routine on dirhandle. pos must be a value returned by telldir. This function has the same caveats about possible directory compaction as the corresponding system library routine.

from perl in a nutshell