For our purposes a file is a line of characters. After a bunch of read and/or write operations we need to tell where are we on that line ?

 LOCATION = tell FILEHANDLE

We might also want to move within that file

 seek FILEHANDLE, OFFSET, WHENCE
 
 WHENCE:
     0 from beginning of file
     1 from current location
     2 from end of file
 OFFSET: 
     +/- number of bytes to move

the important values are:

seek $fh, 0,0;    # go to the beginning of the file
seek $fh, 0,2;    # go to the end of the file