I guess it depends: mapping it to a different value, as in bool ? 1 : 0, will definitely make it more clear (and also force scalar context). But using scalar is better than not using it at all, since if you've got a hash { moo => $vol =~ m/^HOLDING/, foo => 'bar' } that's asking for trouble (and in some cases, security holes, like with CGI.pm's param).

Update: Corrected the example hash