I have to agree with turnstep's first suggestion, since that's the way I code CGI in general. When doing any real work behind the scenes, use a script that redirects the user to a static version of the output to avoid the refresh problem.

In your case, if you're interested in having just one script, make it callable in the default way (which just displays the current value of the counter), the incrementor way (which increments the counter then redirects to the default way), and the reset way (which resets and redirects).

Here's a simple example:

#!perl -w
use strict;
use CGI qw( :standard );
use CGI::Carp qw( fatalsToBrowser ); 
$|=1;
my $count = 0;
if( -e 'cnt.tmp') and not param('Start Over') )
{
 open COUNT, 'cnt.tmp' or die "Failed to open cnt.tmp, $!\n";
 while(<COUNT>)
 {
   if( /^\s*(\d+)\s*$/ )
   {
     $count = $1;
     last
   }
 }
 close COUNT or die "Failed to close cnt.tmp, $!\n";
}
if (param('Again') or param('Start Over') 
{
 open COUNT, '>cnt.tmp' or die "Failed to open >cnt.tmp, $!\n";
 print COUNT ++$count;
 close COUNT or die "Failed to close >cnt.tmp, $!\n";
 print "Location: this.cgi\n\n";
}
else 
{
 print header, start_html('Simple Counter'), "\n";
 print start_form(),
     "Count equals $count",
     br(), "\n",
     submit( -name=>"Again" -value=>"Again"),
     submit( -name=>"Start Over", -value=>"Start Over" ),
     end_form(), "\n";
 print end_html();
}
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