This is the way I'd do it, which only uses core modules.

#!/usr/bin/perl

use warnings;
use strict;
use File::Copy;
use File::Path qw(make_path);
use File::Spec::Functions;
use File::Basename;

my $dir = 'C:/dev';
my @files = grep { ! -d } <$dir/*>;

FILE:
foreach my $file (@files) {
    my ($name, $path, $suffix) = fileparse($file, qr/\.[^.]*/);
    $suffix or do {
        warn "$name does not have an ext\n";
        next FILE;
    };
    $suffix =~ s/\.//;  # (optional) strip leading . 
    my $subdir = catdir($path, $suffix);
    make_path($subdir) unless -d $subdir;
    move($file, $subdir) or warn "Failed to move $file to $subdir <$!>
+\n";
}
[download]

EDIT: If you have spaces in the source path, you will probably need to use quotes when building @files.

Change grep { ! -d } <$dir/*> to grep { ! -d } <"$dir/*">