yet another way (not necessarily the best) would be Cache::FileCache (useful for many other things such as caching database query results). One downside (or upside) is you don't (readily--i think it throws it under /tmp/ somewhere) have the filename, so can't do "cat counter.txt" to check it.

  use Cache::FileCache;
  my $cache = new Cache::FileCache( { namespace=>"my_program", auto_pu
+rge_on_get=>1 } );
  my $cacheKey = 'ct';
  my $value = $cache->get( $cacheKey ) || 0;
  $value++;
  $cache->set( $cacheKey, $value, $EXPIRES_NEVER );
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