Out of curiosity, what does phrasing it in that way buy you?

I thought maybe you were gaining an advantage from the short circuit of && so I wrote a benchmark, but the times came back so close together that the difference is easily attributed to background processes. So I ran the deparser and found that perl converts this to an if(){} structure, which is (as you said) easier to read.

E:\Projects>perl -MO=Deparse -we "my $s; $_ && do { $s = $_ }"
my $s;
if ($_) {
    $s = $_;
}
-e syntax OK
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