The easiest approach in my opinion would be to just access Gmail via the IMAP interface and then use (say) Net::IMAP::Client (or Mail::IMAPClient) to extract the information you want. With Net::IMAP::Client, you can then, fetch the relevant information via IMAP:

    # fetch message summaries (actually, a lot more)
    my $summaries = $imap->get_summaries([ @msg_ids ]);

    foreach (@$summaries) {
        print $_->uid, $_->subject, $_->date, $_->rfc822_size;
        print join(', ', @{$_->from}); # etc.
    }
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I'm not sure where exactly your problem lies, as you haven't told us and haven't shown any code you've already written. I think that this would be a good next step.