#!/usr/bin/perl

package Hasher;
use Carp;
use strict;
use warnings;

sub new {
        my $class = shift;
        my $self  = { @_ };
        bless ($self, $class);
        return $self;
}

sub hash {
        my $self = shift;
        croak 'file does not exist' if not -e $self->{file};

        my %data;
        $data{count} = 0;
        $data{hash} = {};

        $self->{pre}->(\%data) if $self->_verify('pre');
        open my $fh, '<', $self->{file} or croak "could not open $self->{fi
le}: $!";
        while (<$fh>) {
                chomp;
                $data{record} = $_;
                $self->{loop}->(\%data) if $self->_verify('loop');
                ++$data{count};
        }
        $self->{post}->(\%data) if $self->_verify('post');
        return %{$data{hash}};
}

sub _verify {
        my $self = shift;
        my $key = shift;
        return 1 if (
                exists $self->{$key} &&
                ref($self->{$key}) eq 'CODE'
        );
        return 0;
}

1;

##</code><code>##

#!/usr/bin/perl

use strict;
use warnings;
use Hasher;

my $states = Hasher->new(
        file => 'states',
        loop => sub {
                my $data_ref = shift;
                my ($value, $key) = split ' ', $data_ref->{record}, 2;
                $data_ref->{hash}->{ uc $key } = $value;
        },
        post => sub {
                my $data_ref = shift;
                print "hashed $data_ref->{count} states\n";
        }
);

my %state = $states->hash();

map {
        print "$_ = $state{$_}\n";
} keys %state;