$ perl -Mstrict -wE 'my $h = {foo=>"bar"}; my $c = keys ${$h};'

Experimental keys on scalar is now forbidden at -e line 1.
Type of arg 1 to keys must be hash or array (not scalar dereference) at -e line 1, near "};"
Execution of -e aborted due to compilation errors.

##</code><code>##

$ perl -Mstrict -wE 'my $h = {foo=>"bar"}; my $c = keys $$h;'

Experimental keys on scalar is now forbidden at -e line 1.
Type of arg 1 to keys must be hash or array (not scalar dereference) at -e line 1, near "$h;"
Execution of -e aborted due to compilation errors.

##</code><code>##

$ perl -Mstrict -wE 'my $h = {foo=>"bar"}; my $c = keys %{$h};'


##</code><code>##

$ perl -Mstrict -wE 'my $h = {foo=>"bar"}; my $c = keys %$h;'