$ perl mpj4.pl
file: /home/dan/Desktop/upload/382432_10150873103536275_1105470601_n.jpg
ext: jpg
filename: /home/dan/Desktop/upload/image_1.jpg
file: /home/dan/Desktop/upload/542274_470102786337441_1974797173_n.jpg
ext: jpg
filename: /home/dan/Desktop/upload/image_2.jpg
file: /home/dan/Desktop/upload/safe_image.php.jpeg
ext: jpeg
filename: /home/dan/Desktop/upload/image_3.jpeg
$ cat mpj4.pl
#!/usr/bin/perl -w
use strict;
my $path = '/home/dan/Desktop/upload/';
my @files = <$path*>;
my $counter = 0;

for my $img (@files) {
  $counter++;
  print "file: $img\n";
  my $ext = ($img =~ m/([^.]+)$/)[0];
  print "ext: $ext\n";
  my $filename = "$path" . "image_". "$counter" . '.' . "$ext";
  print "filename: $filename\n";  
  rename ($img, $filename) or warn "couldn't rename $img to $filename:  $!\n";

}

$