The OPed code should work fine with any Perl version:

c:\@Work\Perl>perl -wMstrict -MData::Dump -le
"print qq{perl version: $] \n};
 ;;
 my %my_data = (names => 'AbCdEfGh',  states => 'FooBarBaz');
 my $my_data_ref = \%my_data;
 ;;
 my @all_names = split /(?=[[:upper:]])/, ${ $my_data_ref } { names };
 dd \@all_names;
 ;;
 my @ra = split /(?=[[:upper:]])/, $my_data_ref->{states};
 dd \@ra;
"
perl version: 5.008009

["Ab", "Cd", "Ef", "Gh"]

["Foo", "Bar", "Baz"]
[download]

(5.8 is the earliest I can test.)