BEGIN {
   use vars qw( $WARR );
   $SIG{__WARN__} = sub {
                $WARR .= join ' ',(@_),caller(),"\n";
            };
}
warn "hello";
warn "hooyah";
die "aaah";

# ...
END {
    print "Content-Type: text-html\r\n\r\n <pre> $WARR </pre>";
}