#!/usr/local/bin/perl

use strict;

use CGI qw(:all);
my $file = 'counter.txt';

my $counter = 0;
{
  local *FH;
  open(FH, "+<$file") || die $!;
  flock(FH, 2) || die $!;
  
  $counter = <FH>;
  
  seek(FH, 0, 0);
  truncate(FH, 0);
		
  print FH $counter+1;
  close(FH);
}

print header();
print "counter[$counter]\n";