Perl dropping " at line xxx" from warnings when "\n" is present

[bprew]

Why does perl omit the "at line xxx" when I supply a "\n" at the end of a warning?
Example:

b3n@sdf:~> cat test.pl
#!/usr/bin/perl

warn "foo";

warn "bar\n";
b3n@sdf:~> perl test.pl
foo at test.pl line 3.
bar

This appears to be the same for both perl 5.6.0 (eww) and 5.8.7 (specifically perl, v5.8.7 built for alpha-netbsd-thread-multi)

Is this to allow for exception handling with objects or something similar? I'm assuming this is expected behaviour, but I didn't see any note of it in the warn() perldoc page. I won't lose any sleep over it, but it did strike me as odd.
Thanks
Update: added perl version(s)

[friedo]

It's a feature. die works the same way, e.g.

perl -e 'die "foo"'
perl -e 'die "foo\n"'

It's useful if you want to report a warning or fatal error to a user as opposed to a programmer, since a user woudldn't care about scary line-numbers and such. It doesn't affect passing exception objects, since if you're passing an object do die you won't be passing a string that could contain "\n".

[ww]

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....


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

[ikegami]

It's a simple way of giving the programmer the option of including the line number in the message or not. It is indirectly mentioned ("just like die") in warn's documentation.

[Fletch]

If you look at the docs for die it says:

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.

And warn says "Produces a message on STDERR just like "die", but doesn't exit or throw an exception." Granted that's not explicitly saying "warn will print the current script line number and input line number unless the message ends with a newline". You might submit a documentation patch to p5p adding something like "(see the documentation for C<die> for more details)."

[bprew]

Don't I feel sheepish :)

Thanks for pointing me in the right direction, next time when it says just like 'xxx', I'll got ahead and read the docs for 'xxx'