It's a hash of arrays

%info is a hash

$info{lastnames} is an array reference

To take a page out of Basic debugging checklist tutorial

use Data::Dump;
dd { lastnames => [ qw/ ro sham bo / ] };
__END__
{ lastnames => ["ro", "sham", "bo"] }
[download]

Hmm, lets try that again

use Data::Dump;
my %info;
push @{ $info{lastnames} }, 'ro';
push @{ $info{lastnames} }, 'sham';
push @{ $info{lastnames} }, 'bo';
dd \%info;
__END__
{ lastnames => ["ro", "sham", "bo"] }
[download]

Thats better. Last demo

use Data::Dump;
my %info;
$info{lastnames}[0] = 'ro';
$info{lastnames}[1] = 'sham';
$info{lastnames}[2] = 'bo';
dd \%info;
__END__
{ lastnames => ["ro", "sham", "bo"] }
[download]

Any time you're wondering about something , write yourself a little program like these three :) hashofarrays.01.pl, hashofarrays.02.pl, hashofarrays.03.pl

Does a hash of arrays make sense for your use case, maybe :) maybe @records is a better fit, I can't tell yet