print "What city? Choices are:\n", 
      join(", ", sort keys %data), "\n>";
chomp($city = <>);
my $hr = $data{$city};

print "What table? Choices are:\n",
      join(", ", sort keys %{$hr->{$city}}), "\n>";
chomp($table = <>);
$hr = $hr->{$table};

print "Which group? Choices are:\n",
      join(", ", sort keys %{$hr->{$table}), "\n>";
chomp($grp = <>);
$hr = $hr->{$grp};
...