ummm -- bad man page! down, man page. sit!
ActiveState has no such omission:

perldoc -f warn
and
perldoc -f die

As noted above, warn's doc offers a strong indication that one should also read re die... where, in the second corrected third paragraph one finds:

 If the last element of LIST does not end in a newline, the
 current script line number and input line number (if any) are
 also printed, and a newline is supplied....
[download]

which clearly implies that there's something different about the behavior when \n is present.