RHEL-6 Beta includes aspell but not the dictionaries; the current perl-Test-Spelling package (0.11-5) isn't patched to use hunspell (the patch is already in Fedora; see Bug #508643) and so the module isn't very useful in EL-6.
Please update perl-Test-Spelling to the version from Rawhide.
This request was evaluated by Red Hat Product Management for inclusion in a Red
Hat Enterprise Linux major release. Product Management has requested further
review of this request by Red Hat Engineering, for potential inclusion in a Red
Hat Enterprise Linux Major release. This request is not yet committed for
Red Hat Enterprise Linux 6.0 is now available and should resolve
the problem described in this bug report. This report is therefore being closed
with a resolution of CURRENTRELEASE. You may reopen this bug report if the
solution does not work for you.