$f->Button(-text => "FindSelectionNext", -command => [$t->{'rtext'} => "FindSelectionNext"])

##</code><code>##

########################################################################
# get current selected text and search for the next occurrence
sub FindSelectionNext
{
 my ($w) = @_;
 my $selected;
 eval {$selected = $w->SelectionGet(-selection => "PRIMARY"); };
 return if($@);
 return unless (defined($selected) and length($selected));

 $w->FindNext('-forward', '-exact', '-case', $selected);
}