$ perl -Mstrict -Mwarnings -le '
    sub fun { print "@_" }
    fun(1, url);
    fun(2, -url);
    fun(3, -url, "httpRefer");
    fun(4, -url => "httpRefer");
    fun(5, url, "httpRefer");
    fun(6, url => "httpRefer");
'
Bareword "url" not allowed while "strict subs" in use at -e line 3.
Bareword "url"¬ allowed while "strict subs" in use at -e line 7.
Execution of -e aborted due to compilation errors.