1st time:
Fields 1,2,3 = a,b,c (Click Insert)
textarea = abc
2nd time:
Fields 1,2,3 = x,y,z (Click Insert)
textarea = abcxyz

##</code><code>##

print $query->start_multipart_form("POST", "test");
print "Field Name:";
print $query->textfield(-name=>'FieldOne', -size=>25);
print "Field Type:";
print $query->textfield(-name=>'FieldTwo', -size=>25);
print "Field Length:";
print $query->textfield(-name=>'FieldThree', -size=>25);
print "<br>" . $query->submit('Insert Field');
print $query->endform();

$testText = $query->param('SPCtext') . $query->param('FieldOne') . $query->param('FieldTwo') . $query->param('FieldThree');

print $query->start_multipart_form("POST", "test");
print $query->textarea(-name=>'SPCtext', -cols=>50, -rows=>10, -value=>$testText);
print $query->submit('Save');
print $query->endform();