#!/usr/bin/perl -w

use File::Find;
use strict;

my $dir = '/path/to/dir/';

my $oldestfile = 0;
my $filename = "No BOT REPORT: ERROR";

finddepth(\&oldfile, $dir);
print "oldest file = " , $filename,$/;

sub oldfile {
    return unless (/BOT/);
    my $mtime = -M $_;
    if ($mtime > $oldestfile) {
        $filename = $File::Find::name;
        $oldestfile = $mtime;
    }
}