~/perl5/perlbrew/perls/perl-5.16.0/bin/perl test.pl
ä =~           qr/(?^u:\N{U+00e4})/  == true
ä =~          qr/(?^u:\N{U+00e4}+)/  == true
ä =~                 qr/(?^u:\xe4)/  == true
ä =~                qr/(?^u:\xe4+)/  == true
ä =~         qr/(?^u:[\N{U+00e4}])/  == true
ä =~        qr/(?^u:[\N{U+00e4}]+)/  == false
ä =~               qr/(?^u:[\xe4])/  == true
ä =~              qr/(?^u:[\xe4]+)/  == true
ä =~                    qr/(?^u:ä)/  == true
ä =~                   qr/(?^u:ä+)/  == true
ä =~                  qr/(?^u:[ä])/  == true
ä =~                 qr/(?^u:[ä]+)/  == false