DB<20> p prototype "CORE::keys"
\[%@]
  DB<21> p keys @a

  DB<22> p keys %a

  DB<23> p keys $a
Experimental keys on scalar is now forbidden at (eval 32)[c:/Strawberry/perl/lib/perl5db.pl:738] line 2.
Type of arg 1 to keys must be hash or array (not scalar dereference) at (eval 32)[c:/Strawberry/perl/lib/perl5db.pl:\
738] line 2, at EOF

  DB<24>

##</code><code>##

  DB<26> %h1=(a=>1)

  DB<27> %h2=(b=>2)

  DB<28> x @all_keys = keys %h1, keys %h2
0  'a'
1  'b'
  DB<29>