#!/usr/bin/perl -w
 
use strict;
 
my $path_to_dir = shift;
dir("$path_to_dir");
 
sub dir {
  opendir(DIR,"$_[0]");
  my @list_of_files = readdir(DIR);
  foreach(@list_of_files) {
   if($_ ne "." && $_ ne "..") {
    if(-d "$_[0]/$_") {
        dir("$_[0]/$_");
    }
    else {
        rename "$_[0]/$_","$_[0]/"."\L$_";
    }
   }
  }
}