Add some more tests verifying correct behavior of subpattern- and bac…

…k-reference cooperation.

test/perltestdata

@@ -14453,3 +14453,21 @@ foo)" nil nil nil nil "foofoo" t nil nil)
 (1782 "\"xzzzax\" =~ /(?<=b(?&regOne)|zzz)(?<regOne>a)/" "(?<=b(?&regOne)|zzz)(?<regOne>a)" nil nil nil nil "xzzzax" t nil nil)
 (1783 "\"fofof\" =~ /(.)((o)\\1)(?2)/" "(.)((o)\\1)(?2)" nil nil nil nil "fofof" nil "fofof" ("f" "of" "o"))
 (1784 "\"fofog\" =~ /(.)((o)\\1)(?2)/" "(.)((o)\\1)(?2)" nil nil nil nil "fofog" nil nil nil)
+(1785 "\"fofof\" =~ /(?<regOne>.)(?<regTwo>(o)\\k<regOne>)(?&regTwo)/" "(?<regOne>.)(?<regTwo>(o)\\k<regOne>)(?&regTwo)" nil nil nil nil "fofof" nil "fofof" ("f" "of" "o"))
+(1786 "\"fofog\" =~ /(?<regOne>.)(?<regTwo>(o)\\k<regOne>)(?&regTwo)/" "(?<regOne>.)(?<regTwo>(o)\\k<regOne>)(?&regTwo)" nil nil nil nil "fofog" nil nil nil)
+(1787 "\"ffff\" =~ /(.)(((?5))(\\1))((?4))/" "(.)(((?5))(\\1))((?4))" nil nil nil nil "ffff" nil nil nil)
+(1788 "\"ffff\" =~ /(?<regOne>.)(((?&regFive))(?<regFour>\\k<regOne>))(?<regFive>(?&regFour))/" "(?<regOne>.)(((?&regFive))(?<regFour>\\k<regOne>))(?<regFive>(?&regFour))" nil nil nil nil "ffff" nil nil nil)
+(1789 "\"fooo\" =~ /(.)(((?5))(\\3))((?4))/" "(.)(((?5))(\\3))((?4))" nil nil nil nil "fooo" nil nil nil)
+(1790 "\"fooo\" =~ /(.)((?<regThree>(?&regFive))(?<regFour>\\k<regThree>))(?<regFive>(?&regFour))/" "(.)((?<regThree>(?&regFive))(?<regFour>\\k<regThree>))(?<regFive>(?&regFour))" nil nil nil nil "fooo" nil nil nil)
+(1791 "\"oo\" =~ /(?1)((.)\\2)?/" "(?1)((.)\\2)?" nil nil nil nil "oo" nil "oo" nil)
+(1792 "\"aa\" =~ /(?1)((.)\\2)?/" "(?1)((.)\\2)?" nil nil nil nil "aa" nil "aa" nil)
+(1793 "\"oo\" =~ /(?&regOne)(?<regOne>(?<regTwo>.)\\k<regTwo>)?/" "(?&regOne)(?<regOne>(?<regTwo>.)\\k<regTwo>)?" nil nil nil nil "oo" nil "oo" nil)
+(1794 "\"aa\" =~ /(?&regOne)(?<regOne>(?<regTwo>.)\\k<regTwo>)?/" "(?&regOne)(?<regOne>(?<regTwo>.)\\k<regTwo>)?" nil nil nil nil "aa" nil "aa" nil)
+(1795 "\"ffff\" =~ /(?1)((.)\\2)/" "(?1)((.)\\2)" nil nil nil nil "ffff" nil "ffff" ("ff" "f"))
+(1796 "\"ffff\" =~ /(?&regOne)(?<regOne>(?<regTwo>.)\\k<regTwo>)/" "(?&regOne)(?<regOne>(?<regTwo>.)\\k<regTwo>)" nil nil nil nil "ffff" nil "ffff" ("ff" "f"))
+(1797 "\"ffffff\" =~ /(?1)((.)(?3)(\\2))/" "(?1)((.)(?3)(\\2))" nil nil nil nil "ffffff" nil nil nil)
+(1798 "\"ffffff\" =~ /(?&regOne)(?<regOne>(?<regTwo>.)(?&regThree)(\\k<regTwo>))/" "(?&regOne)(?<regOne>(?<regTwo>.)(?&regThree)(\\k<regTwo>))" nil nil nil nil "ffffff" t nil nil)
+(1799 "\"foffoff\" =~ /(.)(?2)((.)(?4)(\\1))/" "(.)(?2)((.)(?4)(\\1))" nil nil nil nil "foffoff" nil nil nil)
+(1800 "\"foffoff\" =~ /(?<regOne>.)(?&regTwo)(?<regTwo>(.)(?&regFour)(?<regFour>\\k<regOne>))/" "(?<regOne>.)(?&regTwo)(?<regTwo>(.)(?&regFour)(?<regFour>\\k<regOne>))" nil nil nil nil "foffoff" nil nil nil)
+(1801 "\"fffffff\" =~ /(.)(?2)((\\1)(?4)(\\1))/" "(.)(?2)((\\1)(?4)(\\1))" nil nil nil nil "fffffff" nil nil nil)
+(1802 "\"fffffff\" =~ /(?<regOne>.)(?&regTwo)(?<regTwo>(\\k<regOne>)(?&regFour)(?<regFour>\\k<regOne>))/" "(?<regOne>.)(?&regTwo)(?<regTwo>(\\k<regOne>)(?&regFour)(?<regFour>\\k<regOne>))" nil nil nil nil "fffffff" nil nil nil)

test/perltestinput

@@ -4279,3 +4279,51 @@ foo)/
 /(.)((o)\1)(?2)/
     fofof
     fofog
+
+/(?<regOne>.)(?<regTwo>(o)\k<regOne>)(?&regTwo)/
+    fofof
+    fofog
+
+/(.)(((?5))(\1))((?4))/
+    ffff
+
+/(?<regOne>.)(((?&regFive))(?<regFour>\k<regOne>))(?<regFive>(?&regFour))/
+    ffff
+
+/(.)(((?5))(\3))((?4))/
+    fooo
+
+/(.)((?<regThree>(?&regFive))(?<regFour>\k<regThree>))(?<regFive>(?&regFour))/
+    fooo
+
+/(?1)((.)\2)?/
+    oo
+    aa
+
+/(?&regOne)(?<regOne>(?<regTwo>.)\k<regTwo>)?/
+    oo
+    aa
+
+/(?1)((.)\2)/
+    ffff
+
+/(?&regOne)(?<regOne>(?<regTwo>.)\k<regTwo>)/
+    ffff
+
+/(?1)((.)(?3)(\2))/
+    ffffff
+
+/(?&regOne)(?<regOne>(?<regTwo>.)(?&regThree)(\k<regTwo>))/
+    ffffff
+
+/(.)(?2)((.)(?4)(\1))/
+    foffoff
+
+/(?<regOne>.)(?&regTwo)(?<regTwo>(.)(?&regFour)(?<regFour>\k<regOne>))/
+    foffoff
+
+/(.)(?2)((\1)(?4)(\1))/
+    fffffff
+
+/(?<regOne>.)(?&regTwo)(?<regTwo>(\k<regOne>)(?&regFour)(?<regFour>\k<regOne>))/
+    fffffff