Current Perl documentation can be found at perldoc.perl.org.

Here is our local, out-dated (pre-5.6) version:

Use the Mail::Folder module from CPAN (part of the MailFolder package) or the Mail::Internet module from CPAN (also part of the MailTools package).

   # sending mail
    use Mail::Internet;
    use Mail::Header;
    # say which mail host to use
    $ENV{SMTPHOSTS} = 'mail.frii.com';
    # create headers
    $header = new Mail::Header;
    $header->add('From', 'gnat@frii.com');
    $header->add('Subject', 'Testing');
    $header->add('To', 'gnat@frii.com');
    # create body
    $body = 'This is a test, ignore';
    # create mail object
    $mail = new Mail::Internet(undef, Header => $header, Body => \[$body]);
    # send it
    $mail->smtpsend or die;

Often a module is overkill, though. Here's a mail sorter.

    #!/usr/bin/perl 
    # bysub1 - simple sort by subject
    my(@msgs, @sub);
    my $msgno = -1;
    $/ = '';                    # paragraph reads
    while (<>) {
        if (/^From/m) {
            /^Subject:\s*(?:Re:\s*)*(.*)/mi;
            $sub[++$msgno] = lc($1) || '';
        }
        $msgs[$msgno] .= $_;
    } 
    for my $i (sort { $sub[$a] cmp $sub[$b] || $a <=> $b } (0 .. $#msgs)) {
        print $msgs[$i];
    }

Or more succinctly,

    #!/usr/bin/perl -n00
    # bysub2 - awkish sort-by-subject
    BEGIN { $msgno = -1 }
    $sub[++$msgno] = (/^Subject:\s*(?:Re:\s*)*(.*)/mi)[0] if /^From/m;
    $msg[$msgno] .= $_;
    END { print @msg[ sort { $sub[$a] cmp $sub[$b] || $a <=> $b } (0 .. $#msg) ] }