'^.{9}abc.*\n'm 123\nabcabcabcabc\n y - -
^(a)?a$ a y -$1- --
^(a)?(?(1)a|b)+$ a n - -
+^(a\1?)(a\1?)(a\2?)(a\3?)$ aaaaaa y $1,$2,$3,$4 a,aa,a,aa
+^(a\1?){4}$ aaaaaa y $1 aa
+^(0+)?(?:x(1))? x1 y - -
+^([0-9a-fA-F]+)(?:x([0-9a-fA-F]+)?)(?:x([0-9a-fA-F]+))? 012cxx0190 y - -