whats the 'right way' to test for output on STDERR

[Jim Cromie]

hi all,

im patching a module that uses Test::More, and I want to include a test
to prove that a carp is being called when function args are wrong.
I half-expected to find a stderr_like()  that would do the trick.

I ended up with this;

{
 local $SIG{__WARN__} = sub {
   return if $_[0] =~ /following args are not recognized/;
   warn $_[0];
};
like ( $proxy = HTTP::Proxy->new( junk => 'not allowed' ),
   qr/HTTP::Proxy/, "ok");
}
which works to an extent, but isnt very clean, and appears to rely on 
Test::More
watching STDERR to detect problems, and an obtuse suppression of the
expected err.

This module also uses STDERR for its own purposes (by default),
that fact hasnt broken the above, but might be a confounding issue for
a general solution.
Is such a function a worthwhile addition to any of Test::* ?

tia.