bend the rules differently.

I wouldn't exactly call it "bending the rules". For perl or the other two.

I read it that perl uses a minimal munch approach at that point of the syntax and hence sees:

( ( $fred == 42) ? ( $config = 'k1') : ( $config ) ) = 'k2';
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Whereas the other two use a maximal munch approach and so see:

( $fred == 42 ) ? ( $config = 'k1' ) : ( $config = 'k2' );
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I think the use case for Perl's way is using the ternary as the lvalue target of assignment. Something like:

$lo = $hi = 0; 
$x = 7; $mid = 5; 

$x < $mid ? $lo : $hi = $x; 

print "lo:$lo hi:$hi";;
lo:0 hi:7
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Can Ruby or PHP do that?