((?>[^()]+)|\([^()]*\))+ ((abc(ade)ufh()()x y $& abc(ade)ufh()()x
(?<=x+)y - c - Variable length lookbehind not implemented
a{37,17} - c - Can't do {n,m} with n > m
+a{37,0} - c - Can't do {n,m} with n > m
\Z a\nb\n y $-[0] 3
\z a\nb\n y $-[0] 4
$ a\nb\n y $-[0] 3
/^\s*i.*?o\s*$/s io\n io y - -
# As reported in #59168 by Father Chrysostomos:
/(.*?)a(?!(a+)b\2c)/ baaabaac y $&-$1 baa-ba
+# [perl #60344] Regex lookbehind failure after an (if)then|else in perl 5.10
+/\A(?(?=db2)db2|\D+)(?<!processed)\.csv\z/xms sql_processed.csv n - -
+/\N{U+0100}/ \x{100} y $& \x{100} # Bug #59328
+[\s][\S] \x{a0}\x{a0} nT - - # TODO Unicode complements should not match same character
+
+# was generating malformed utf8
+'[\x{100}\xff]'i \x{ff} y $& \x{ff}
+
+((??{ "(?:|)" }))\s C\x20 y - -