'-l' has a dual nature - on input it behaves like chomp(), automatically removing newline characters, while on output, as we've seen, it becomes the anti-chomp, adding newlines.
. . .
-0 . . . Using this is like messing with $/ in a script . . .

For completeness, I would mention that '-l' is implemented by messing with $\ and $/:

$ perl -MO=Deparse -le ''
-e syntax OK
BEGIN { $/ = "\n"; $\ = "\n"; }
();
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Also, you can specifiy a different character (in octal) on the command line for -l to use for $\ (output records):

$ perl -MO=Deparse -l001 -e ''
-e syntax OK
BEGIN { $/ = "\n"; $\ = "\001"; }
();
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-0 can also take an octal number, but this time it sets $/ (input records):

$ perl -MO=Deparse -0001 -e ''
-e syntax OK
BEGIN { $/ = "\001"; $\ = undef; }
();
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