If I were to use a file as opposed to a DB, I'd most definitely use JSON. Cross-platform, cross-language, and web API ready.

codes.json

{
    "91280": "CA",
    "61682": "NY",
    "23823": "WA"
}
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Perl script:

use warnings;
use strict;

use JSON;

my $file = 'codes.json';

my $data;

{
    local $/;
    open my $fh, '<', $file or die $!;
    my $json = <$fh>;
    $data = decode_json $json;
}

print "$_: $data->{$_}\n" for sort keys %$data;
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Output:

23823: WA
61682: NY
91280: CA
[download]