Since it's a developer release, you won't get it if you upgrade in CPAN or CPANPLUS. You have to download and install manually.
actually you can just use CPAN: 
$ cpan
cpan[1]> ls andya
[...]
  117943 2007-09-03 ANDYA/Test-Harness-2.99_01.tar.gz
[...]
cpan[2]> install ANDYA/Test-Harness-2.99_01.tar.gz

[download]

In reply to Re: Test::Harness 2.99_01 Released by tinita
in thread Test::Harness 2.99_01 Released by Ovid

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