Using the seek function to seek a byte range

So I'm trying to use the seek function to seek a couple of lines of the file without going to the end of the file. Just trying to stay within a certain byte range. Here is my code.

Code:

#!/usr/local/bin/perl
print "content-type: text/html\n\n";
open (FILE, "< file.txt") or die("File not found");
seek FILE, 21,0;
while(<FILE>)
{
   print;
}
close(FILE);
exit;

What would I need to do to only stay within a certain byte range and display the text only in that byte range without going to the end of the file. I have looked all over but can't seem to figure out how to do this without going to the end of the file.

 

Code:

#!/usr/local/bin/perl
print "content-type: text/html\n\n";
open (FILE, "< file.txt") or die("File not found");
seek FILE, 0,21;
while(<FILE>)
{
   print;
}
close(FILE);
exit;

http://perldoc.perl.org/functions/seek.html