evaluate entered postcodes against perl array

Question

I have an array which contains the starting 2 characters of postcode areas in perl like so:

@acceptedPostcodes = ("CV", "LE", "CM", "CB", "EN", "SG", "NN", "MK", "LU", "PE", "ST", "TF", "DE", "WS");

I have a search box where a user will type in part or a full post code. I need to check if the post code they entered started with one of the elements of the array so for example if they entered 'CV2 1DH' it would evaluate to true and if they entered something like 'YO1 8WE' it would evalute to false as it doesn't start with one of the array values.

Now this would be easy to do in PHP for me but Perl isnt something im too good at and so far my efforts havn't been very fruitful.

Any idea peeps?

Answer 1

If your list of accepted postcodes is large enough that performance in the matching code is an actual concern (it probably isn't), you'd probably be better off using a hash lookup instead of an array anyhow:

#!/usr/bin/perl

use strict;
use warnings;

my %accepted_postcodes = ("CV" => 1, "LE" => 1, "CM" => 1, "CB" => 1, "EN" => 1, "SG" => 1, "NN" => 1, "MK" => 1, "LU" => 1, "PE" => 1, "ST" => 1, "TF" => 1, "DE" => 1, "WS" => 1);
# Or, to be more terse:
# my %accepted_postcodes = map { $_ => 1 } qw(CV LE CM CB EN SG NN MK LU PE ST TF DE WS);

my $postcode = "CV21 1AA";

if (exists $accepted_postcodes{substr $postcode, 0, 2}) {
    print "$postcode is OK\n" ;
} else {
    print "$postcode is not OK\n";
}

This method will work fine with 5.8.8.

Answer 2

Smart Match (~~) is your friend here (after you use substr to get the first two letters from the entered string.

#!/usr/bin/perl

use strict;
use warnings;
use v5.10;

my @acceptedPostcodes = ("CV", "LE", "CM", "CB", "EN", "SG", "NN", "MK", "LU", "PE", "ST", "TF", "DE", "WS");

my $postcode = "CV21 1AA";

if ((substr $postcode, 0, 2) ~~ @acceptedPostcodes) {
    say "$postcode is OK" ;
} else {
    say "$postcode is not OK";
}