#!/usr/bin/perl -w

use strict;
use File::stat;
my $mytime=(time);
my $file_stat;
...
opendir(DIR, $all_session) or die "Couldn't open directory, $!";
  while (my $sessions = readdir DIR) {
      # Use a regular expression to ignore files beginning with a period
      next if ($sessions =~ m/^\./);
      next if ($sessions !~ /^cgisess_[a-f0-9]{32}$/);
      #if( -M qq{$all_session/$sessions} > 360){ # 6 minutes
          #print "Del these session files: $sessions<br>";
       #}
     if ($file_stat = (stat $sessions)[9]){
          if ($file_stat >= ($mytime - 300)) {
              print "File older than 5min found. The file name is $sessions";
              last;
          }
      }
    }
closedir DIR;
...