I find it significantly easier and faster to parse the intent.

Could you quantify (in some fashion) what you mean by "significantly easier and faster"?

my $mol = ( $n == 42 ) ? 'forty two' : '';
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my $mol = '';
 $mol = 'forty two'
     if  42 == $n;
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I find your version quite horrible to parse.

• Is that one statement or three?

  Oh! It's two!

• And why is it (are they) all squished up like that?

  It looks like the the code-wrap routine has been given some ridiculously narrow width limit.

• Why is he comparing a literal against a variable?

  Is the literal's value likely to suddenly change?

  (Yes. I am aware of the justifiction for the backward logic. :)

As for your last example, I find it almost incredulous that you would code that; and almost impossible to parse without reformatting it.

Why not just:

my $mol =  defined $n ? ( $n == 42 ? 'fourty two' : '' ) : 'n/a';
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I also find the concentration on the minutia of single statements far less important than the overall flow of the code.

That is, when scanning the code, I only need to recognise that $mol has been initialised, and then the next step and the next. I'll only be concerned with what it was initialised to once I understand the overall flow; and if I suspect that might be the source of the problem I'm looking for, or otherwise needs closer inspection.

I don't need to know all the details of each line (or 3 lines!) of code from an instantaneous glance. If I have to read the line twice to understand what it does -- maybe take 2 seconds instead of 1/2 a second -- it is no biggy in the scheme of things. But understanding the overall flow of the subroutine or block is far more important, and that -- for me at least -- means being able to see as much of that subroutine or block as -- clearly defined steps -- as possible. Which is why I infinitely prefer the one line versions to your 3 or 5 line examples.