#!/usr/bin/perl

use strict;
use DB_File;

my $base    = '/some/dir';     # dir to check
my $data    = '/some/file.db'; # file name cache
my $sleep   = 100;             # how long to sleep for
my $maxtime = 86400;           # max time before key removal

while (1) {
#
# we need to tie and untie each time just to be safe due
# to file caching and flushing, which sometimes doesnt 
# happen untill the file has been untied. 
# If another monk can help here that would be nice.
#
   tie(my %files, 'DB_File', $data, O_RDWR, 0644)
      or die "Cant tie $data: $!\n";

   opendir(BASE, $base) or die "Cant open dir $base: $!\n";
   for ( grep(!/^\./, readdir BASE) ) { # avoid . and .. :)
      if ( $files{$_} ) {
         $files{$_} = time();

      } else {
         do_something();
         $files{$_} = time();
      }
   }
   closedir(BASE);

   for ( keys %files ) {
# remove the file if it hasnt been around for a week
      delete($files{$_}) if ($files{$_} >= $maxtime);
   }
   untie(%files);

   sleep $sleep;
}
[download]

use perl;