TL;DR

MIME::Parser and Email::Address::XS came to help.

I wanted to analyze an email and, in particular, I wanted to extract the full list of recipients. As a list, I mean.

My inners self let a little groan come out: there’s a plethora of email-related modules in CPAN, many (most?) of which are from the same author and fill different niches with different interfaces, in a quest for the perfect one.

Don’t get me wrong, I admire RJBS and I also resonate with that kind of quest for something that I would have liked to have already found there.

Still, there’s a plethora of modules, and so my groan.

Luckily enough, some 13 years ago I wrote a small reference booklet (still available here) about implementing several clients for the web in Perl. Did I mention that it’s in Italian? No? Well, sorry for the wasted bandwidth, folks.

I will not apologize to Italian-understanding people though, I was clear that the book is from 13 years ago and much of it became obsolete.

So it kind of stuck with me that parsing emails could be done with MIME::Parser. Having the email saved as a file (according to RFC 2822, not the proprietary formats that serve to wall gardens), this is what I resorted to (more or less, I go by memory):

use MIME::Parser;
my $parser = MIME::Parser->new;   # get a parser
$parser->output_to_core(1);       # message is small enough

my $filename = shift(@ARGV);
open my $fh, '<:raw', $filename   # 3-args open for the win!
    or die "open('$filename'): $!";
my $email = $parser->parse($fh);  # gives a MIME::Entity object back
my $headers = $email->head;       # gives a MIME::Head object back

OK, now I only have to extract the recipients, which can appear either in to or cc:

# don't copy-paste this, there's something better ahead
my @recipients = ($headers->get_all('to'), $headers->get_all('cc'));

Only thing is that… the get/get_all methods give back the literal string the header is set to, not the nice list of addresses I was looking for.

Fair enough, so what can we use for that? The list can be broken on multiple lines and parsing addresses is not exactly easy.

Enter Email::Address::XS, which has the right tool for this particular job:

# still not what I was looking for, but might be good for others
use Email::Address::XS 'parse_email_addresses';
my @recipients =
    map { parse_email_addresses($_) }
    map { $headers->get_all($_)     }
    qw< to cc >;

In my case, this was not the definitive solution, because I was collecting results to print out a JSON-encoded string, so having objects of class Email::Address::XS was not exactly what I was after.

This was (or, well, the tested version of this):

use Email::Address::XS 'parse_email_addresses';
my @recipients =
    map { $_->as_string             } # $_->address -> foo@example.com
    map { parse_email_addresses($_) }
    map { $headers->get_all($_)     }
    qw< to cc >;

So there you go, future me: if you ever need this again, please assemble a full program to share with even-more-future-us 🙄

Everybody else stay safe!