I mentioned I would write a post called "Python Is Not an Acceptable Shell". I think it's also clear that Perl isn't an acceptable shell, simply because shell still exists. And awk and sed still exist -- in fact I believe it's common these days to use shell/awk/sed but NOT Perl, which means that Perl fell short of its mission. (I certainly prefer shell/awk/sed to Perl.)
There is overlap between Oil and Perl, which is ironic because I've written probably 100x-1000x the Python code that I have Perl code. But I would say I'm tackling some of the same problems, but not using the same solutions.
An obvious thing is that Oil will not be nearly as line-noisey as Perl, which is the thing that is most often complained about (rightly or not).
Perl also doesn't have some obvious shell constructs like pipelines. I'm pretty sure you just "shell out" for such things, which isn't a good solution.
I've been looking at Perl 6 too, and there is overlap there too. But I honestly think a new shell has more of a chance of being adopted widely than Perl 6. There is apparently still an unresolved schism between Perl 5 and 6:
As far as I can tell, Perl 6 is even further from a shell than Perl 5 is. Python 3 is also less suited for shell-like tasks than Python 2 is (due to its Unicode conventions).