highlightText($TextWidget, \$term, 'selectedTerm', 'regexp');

sub highlightText {
    my($w, $string, $tag, $kind) = @_;
    my $stringw = $$string;
    return unless ref($string) && length($$string);

    my($current, $length) = ('1.0', 0);
    
    $stringw = qr/\b\Q$stringw\E\b/;#creating regex

    while (1) {
	$current = $w->search(-count => \$length, "-$kind", "-nocase", $stringw, $current, 'end');#here I the -nocase causes an issue
	last if not $current;
	$w->tagAdd($tag, $current, "$current + $length char");
	$current = $w->index("$current + $length char");
    }
}