update: the indented block is irrelevant now, with the update in the OP
Your examples are not equivalent. Your "if" case should look something like this:
my $number = do {
if ($logical_test) {
$value
}
else {
0
}
}
Note that there is no automatic assignment of the 0 value. Doesn't make much difference here, ofcourse, but for more complicated cases its possible that those assignments have side-effects, or just take a lot of time.
Anyway, I would not recommend using ?: in very complex statements, because the ? and : tend to get drowned. But then, I would not recommend using statement modifiers in such a case either:
$bla = $some_really_long_calculation_that / $you_just_don_t * $want_to
+_read_all_the_way_to_the_end if $something;