There isn't one at all, obfuscated or otherwise.

The thing that has always prevented anyone from writing such a program is that it's very hard! It's easy to do a really bad job, but to do a good job, you have to be very clever. For example, suppose you see this:

    set bar=`echo $foo | awk '{print $5}' | cut -c1-4`
[download]

The obvious (bad) translation is:

    $bar=`echo $foo | awk '{print \$5}' | cut -c1-4`
[download]

But the right translation is:

    $bar = substr((split($foo))[4], 0, 4);
[download]

Anyway, aside from an April Fool's joke that Randal perpetrated a few years ago, there is no shell-to-perl translator that I know of.