-l "sets $\ to the current value of $/" (see perlrun)

In otherwords, it automatically adds a "\n" to all print statements. I like to use it for short one liners, since it helps keep the output separate from my shell prompt.

Oh, and the options usually aren't counted as keystrokes in one-liner golf. i.e both would score a 16:

#         1234567890123456
perl -le 'print$ENV{SHELL}'
[download]

-Blake