"Thanks Ken for the helpful code ..."

You're welcome.

"With regards changing the form, that won't be happening as explained in Re^2: Split first and last names"

That's new information (only posted an hour or so ago) but does add some clarity.

"... full name (... envelope) ... firstname ... salutation."

Perhaps something along these lines:

#!/usr/bin/env perl

use strict;
use warnings;
use utf8;
use open OUT => qw{:encoding(UTF-8) :std};

my @names = ("Zoë", "Zoë Åcçéñt-Smythe");

my $re = qr{(?x:
    ^
    (
        (
            [\p{Alpha}'_-]+
        )
        [\s\p{Alpha}'_-]*
    )
    $
)};

for my $name (@names) {
    my ($full, $first) = $name =~ $re;
    print "Name:  $name\n";
    print "First: $first\n";
    print "Full:  $full\n";
}
[download]

Output:

Name:  Zoë
First: Zoë
Full:  Zoë
Name:  Zoë Åcçéñt-Smythe
First: Zoë
Full:  Zoë Åcçéñt-Smythe
[download]

Note that I allowed three punctuation characters ('_-); alter as necessary. I know, from earlier posts, that you're across SQL injection issues. Be aware, that between reading data from the web and supplying it to SQL, there may be other code injection issues. Without knowing anything more about your code, that's something you'll need to assess for yourself: I didn't include any validation; but you should.

"As for the database storage..."

I looks like most of that would be covered by "If we need extra information ... we ask for it ...". The majority wouldn't be covered by user input anyway (e.g. nickname, preferred names). Again, something for you to determine using the same principles as above (i.e. limited regex capture, code injection & validation).