obscure implementation details

Disagree. The shape of booleans in Perl 5 is specified behaviour, and is only going to become more explicit in Perl 6.

I would instead suggest that a clearer, more maintainable version might be ($string) x ($cond ? 1 : 0)

If you’re using a ternary anyway, why would you want to throw in an x op? All that does is lose the shortcircuiting, make the code longer, and force some extraneous parens. Just do all the work using the ternary: $cond ? $string : ()

I don’t find either of your original “problem” examples to be particularly onerous

I’d never use the push version. The one with ternaries doesn’t look onerous because there are so many conditional bits that you have no hope of putting it all on a single line anyway, and the lists are simpler than the conditionals, and it’s highly regular, and all. I was trying to come up with an example that can’t be simplified using grep.

I can’t recall the exact code that led me to post the thread on perl6-users which led Larry to nudge me in this direction, but it was a case of injecting a single list into the arguments of a one-liner join, where precedence forced me to parenthesise things, so the version using the ternary absolutely was more ornery than it should have been. With such a short list, it’s more annoying than the example I gave in the root node, because nothing really helps – putting it on a single line makes it unwieldy, breaking it into multiple lines makes it breathlessly verbose, using an extra temporary looks hackish. Sticking an x!! wouldn’t have been ideal, but would certainly read better than all the alternatives.

Makeshifts last the longest.