Your code doesn't compile. You use %{$data}, but the data you show in the POD are an array. From the error, it seems you tried to dereference the zip code as an array ref:

use strict;
my $data = [ '10010' ];
print @{ $data->[0][1] };
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Use Data::Dumper to see what data structures your variables contain.

use Data::Dumper;
print Dumper($data);
print Dumper($data->[0]);
[download]

pop needs an array as the parameter, not a string.