$ perl -wle 'sub x{};@y=x(); print "array" if @y'
(nothing)
$ perl -wle 'sub x{};%y=x();print "hash" if %y'
(nothing)
$ perl -wle 'sub x{1..3};@y=x(); print "array" if @y'
array
$ perl -wle 'sub x{a => 1};%y=x();print "hash" if %y'
hash