use Encode qw(encode decode);
my $enc = 'utf-8'; #in dieser Kodierung ist das Script gespeichert

sub ucfirst_every_word {
  my $s = shift;
  my $text_str = decode($enc, $s);
  $text_str =~ s{\b(\w+)\b}{ucfirst(lc($1))}eg;
  $s= encode($enc, $text_str);
  return $s;
}

$text =~ s/(= .*?KAPITEL.*? =)/ucfirst_every_word($1)/eg;