In fact, why not replace

if(DoIHaveThisData($hashref, 'key2')){
[download]

with

if (exists $hashref->{key2}) {
[download]

A very minor issue with Storable is that it depends on at least the perl version, maybe also on compile-time settings. This may cause trouble when you update perl.

Other serialization formats do not have that specific problem.

Using JSON would make your serialized hash human readable (at least when adding some whitespace).

YAML and Data::Dumper output may contain executable code, reading them back may cause security problems.

Sereal promises to be fast and compact, but it is a binary format like Storable.

XML is bloat, can't store 0x00, *and* has security issues (Billion laughs attack).

If your hash is as simple as shown (no references, just a key-value-store), also consider SQLite with a simple two-column table. (See DBI and DBD::SQLite). As a minor and probably welcome side-effect, the database file will automatically be created at first use.

Alexander

G'day redapplesonly,

"I am working on a Perl (v5.30.0) script that needs to use stateful information from the previous run of the script."

All of your steps, and other design notes, seem spot-on to me. :-)

"But here's the problem: What about the first time the script runs?"

That's a very valid point. I don't use Storable very often, but when I do I encounter the same issue. I usually handle this by dealing with it before runtime execution starts in an INIT block.

Here's a rough example of how I might have written your code (pm_11148149_storable_first_run_0.pl):

#!/usr/bin/env perl

use 5.030;
use warnings;

use Storable;

my ($hashfile, $serial_data_for);
INIT {
    $hashfile = 'pm_11148149_storable_first_run.sto';
    $serial_data_for = -e $hashfile ? retrieve($hashfile) : {};
}

my @keys = qw{key1 key2 key3};
my @vals = qw{data1 data2 data3};
$serial_data_for->@{@keys} = @vals;

store($serial_data_for, $hashfile);
[download]

I added some extra statements for reporting/demo purposes (pm_11148149_storable_first_run_1.pl):

#!/usr/bin/env perl

use 5.030;
use warnings;

use Storable;
use Data::Dump;

warn "Perl version: $^V\n";

my ($hashfile, $serial_data_for);
INIT {
    $hashfile = 'pm_11148149_storable_first_run.sto';
    $serial_data_for = -e $hashfile ? retrieve($hashfile) : {};
}

say 'Serialised data:';
dd $serial_data_for;

my @keys = qw{key1 key2 key3};
my @vals = qw{data1 data2 data3};
$serial_data_for->@{@keys} = @vals;

store($serial_data_for, $hashfile);
[download]

Here's some equivalent output to your sample run:

ken@titan ~/tmp
$ rm pm_11148149_storable_first_run.sto

ken@titan ~/tmp
$ ls -l pm_11148149_storable_first_run.sto
ls: cannot access 'pm_11148149_storable_first_run.sto': No such file o
+r directory

ken@titan ~/tmp
$ ./pm_11148149_storable_first_run_1.pl
Perl version: v5.30.0
Serialised data:
{}

ken@titan ~/tmp
$ ls -l pm_11148149_storable_first_run.sto
-rw-r--r-- 1 ken None 69 Nov 12 13:00 pm_11148149_storable_first_run.s
+to

ken@titan ~/tmp
$ ./pm_11148149_storable_first_run_1.pl
Perl version: v5.30.0
Serialised data:
{ key1 => "data1", key2 => "data2", key3 => "data3" }

ken@titan ~/tmp
$
[download]

Notes:

• I concur with ++choroba's suggestion to use the builtin exists() function directly, rather than rolling your own DoIHaveThisData(). While abstracting functions into subroutines for reuse is often a very good idea, I don't see any benefit in this instance. If you did consider it to be necessary, I'd keep it very simple along the lines of:

  sub DoIHaveThisData {
      my ($hash, $key) = @_;
      return exists $hash->{$key};
  }
  [download]

• You may need to look at "perlref: Postfix Reference Slicing", and perhaps even "perldata: Slices", if you're unfamiliar with how I've populated the hashref.
• A .sto extension, to identify Storable files, is widely used. It's not a requirement; it might qualify as a convention.

#!/usr/bin/perl

use strict; # https://perlmonks.org/?node_id=11148149
use warnings;
use Storable;

my $filename = '/tmp/d.11148149.testfile';

my $hashref = eval { retrieve $filename } || {};
use Data::Dump 'dd'; dd $hashref; # was
$hashref->{+time} = 1; # do something with $hashref...
use Data::Dump 'dd'; dd $hashref; # is now
store $hashref, $filename;
[download]

A while ago I wrote this about serializing a hash. Probably it is still helpful. Regards, Karl