#!/usr/bin/perl

use 5.020;
use strict;
use warnings;

use Sereal;
use Fcntl ':flock';

my $cachename = 'validator.cache';

my %validator;

sub fetch_validator {
    if ( open my $CACHE, '<', $cachename ) {
        binmode $CACHE;
        my $data = <$CACHE>;
        close $CACHE or die;

        my $sereal = Sereal::Decoder->new();
        if ( $sereal->looks_like_sereal($data) ) {
            my $VAR1 = $sereal->decode($data);
            %validator = %{$VAR1};
        }
        else {
           warn "No SERAL data";
        }

        return %validator;
    }
}

sub put_validator {
    if ( open my $CACHE, '>', $cachename ) {
        truncate $CACHE, 0;
        seek $CACHE, 0, 0;
        flock $CACHE, LOCK_EX;
        binmode $CACHE;

        my $sereal = Sereal::Encoder->new();
        my $VAR1   = \%validator;

        my $data = $sereal->encode($VAR1);

        print $CACHE $data;
        close $CACHE or die;

        return %validator;
    }
}

use Digest::MD5 qw(md5_hex);

for ( 1 .. 1_000 ) {
    my $d = $_;
    $validator{ 1000 + $d }{ time + rand $d } = md5_hex(time);
    put_validator();

    fetch_validator();
}