if ( -e "$path/$filename" ) { 
           my $unique = unique();
           $filename=~s/^([^_]+_)(.*)(\.\w{3})\z/$1.$2.$unique.$3/eg;
           rename( "$path/$filename", "$path/$filename");
           unlink($filename);
         }
}
sub unique {
my ($sec, $min, $hour, $mday, $mon, $year, $wday, $yday, $isdst) = localtime(time);
$mon++;
$year = $year + 1900;
my $timestamp = sprintf "%4d%02d%02d%02d%02d%02d", $year,$mon,$mday,$hour,$min,$sec;
my $rand = (rand 10000);
$rand = int($rand);
my $unique = "$timestamp$rand";
}