You would need to be consistent and hence indent the conditional within every if-and-while-and-etc in the same way.

True but on the other hand, we can write:

Or, since we do Perl:

And few will complain that the body of the sub and the if isn't indented; so I guess the same applies for the conditions. I have indented conditions as shown here and consider this layout a good practice, be it with tabs or spaces. But there's no need to do it always.