1<Macro warnings $u $n $u1 $n1 $u2 $n2> 2 Warning "many warnings! $u $u1 $u2" 3 # $n $n1 $n2 4</Macro> 5 6# warn about unused arguments 7Use warnings 1 2 3 4 5 6 8 9# may warn about empty arguments? 10Use warnings '' '' '' '' '' '' 11 12Error "done!" 13