(Hope this is the right spot for this!) Pythonists complain that Perl doesn't have an interactive mode, but of course you can easily make one. However other examples I have seen were 20 line scripts, a little while ago I made up this one liner (which I tend to stash in a minimal shell script called ip, on every machine I use): 
perl -ne 'print join(",", eval),"\n> "'

[download]
(Of course half that is just for prettification, if you don't mind ugly you can just say perl -ne 'print eval'.) It does pretty much everything you hope (provided your shell handles up arrow history for you). An example session: 
./ip
$a=2
2
> $a**10
1024
> $a *= 3
6
> sprintf '%lx', ~$a
fffffff9
> use Digest::SHA 'sha256_hex'

> sha256_hex 10
4a44dc15364204a80fe80e9039455cc1608281820fe2b24f1e5233ade6af1dd5
> exit

[download]
Although also very useful for testing small confusions about syntax, I've found it so handy as a sort of super calculator that I now keep an instance running all the time.

In reply to Interactive perl by Securiger

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