Solved: 
use strict;

use Prima qw( Application VB::VBLoader);
my $ret = Prima::VBLoad('H:\My Documents\PERL\Prima\Concepts.fm',
    Populate => {onClick => sub{trythis("writing ...")}},
);
die "$@\n" unless $ret;

sub trythis {
    my ($x) = @_;
    $ret-> textbox-> set(text => $x);
}

our $global = $ret-> textbox-> text;
print "$global\n";
$ret-> execute;

[download]
Just needed to do some trial and error testing and it came out.

In reply to novice Prima question by briannz556

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
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