The principal solution is to export the number of the last entry through post, i.e.: a href="myscript.cgi?entry=5"
Then you can use the following routine in your script:

if ($entry >=5) {my $backnum= $entry-5} else {my $backnum=0};
my $nextnum=$entry+5;
while ($entry % 5) {
#do your output stuff ;
$entry++;
  if ($backnum) {
                   print "<a href=\"myscript.cgi?$backnum\">Previous</
+a>"};
};

print "<a href=\"myscript.cgi?$nextnum\">Next</a>"};
#other stuff...
[download]

However, if you would not use CGI module at all, you may parse parameters as $ARGV[0]
You might make a check for the nnumber of entries not to make your Next link to the enmpy page.
--
With best regards
Maqs.