Hey peterb, are you looking for something like this?

#!/perl/bin/perl -w
use strict;
use Data::Dumper;

my $data = [
  { _name     => "John Smith",
    _address1 => "123 Foo St.",
    _address2 => "Apt 5",
  },
  { _name     => "Brigitte Nelson",
    _address1 => "150 Park Pl.",
    _address2 => "Suite 223",
  },        
];


my @cols = qw / _name  _address1  _address2  /;

for my $customer (@$data) {
  for my $col (@cols) {
    printf "%s => %s\n", $col, $customer->{$col} || "<empty>";
  }
}
[download]

Updated: Added <empty> string in case of emptiness...