%foo = HASH(0x1ab298c) { 2/8 } = ( foo => 1,baz => 3,bar => 2 )
foo => 1 is gone.
%foo = HASH(0x1ab298c) { 1/8 } = ( baz => 3,bar => 2 )
baz => 3 is gone.
%foo = HASH(0x1ab298c) { 1/8 } = ( bar => 2 )
bar => 2 is gone.
%foo = HASH(0x1ab298c) { 0 } = (  )