Simplest I could come up with is (more or less the same what you did)

$ perl -MDP -wE'my%x;$x{$_}++ for "iowq john stepy andy anne alic bert
+ stepy anne bert andy step alic andy" =~ m/(\w+)/g;DDumper\%x'
{   alic             => 2,
    andy             => 3,
    anne             => 2,
    bert             => 2,
    iowq             => 1,
    john             => 1,
    step             => 1,
    stepy            => 2
    }
[download]

edit: and here the code inside the regex:

$ perl -MDP -wE'my%x;()="iowq john stepy andy anne alic bert stepy ann
+e bert andy step alic andy" =~ m/(\w+)(?{$x{$^N}++})/g;DDumper\%x'
[download]