#! perl
use strict;
use warnings;
use Data::Dump;

my %HASH;
$HASH{keyA}{keyB} = [1 .. 4];
dd \%HASH;

my $array_ref = $HASH{keyA}{keyB};

delete $HASH{keyB};
delete $HASH{keyA};

$HASH{keyB}{keyA} = $array_ref;
dd \%HASH;