use File::Find;
my @dirs = qw(.);

find( sub{
 return if $File::Find::name eq $File::Find::topdir;
 $File::Find::prune=1, return if -d;
 if ((my $newname = $_) =~ tr/ /./) {
  print "Renaming $File::Find::name to $newname\n";
  rename $_, $newname or die "Can't rename $_: $!";
 }
}, @dirs);