/
(?x:#sds
)
(?#sdsa)
#sda
(?x) # extended mode)
(?<!\\) # no escape in before paren)
(?: # begine or end alternation noncap group)
(?<begin>\( # begining pattern paren)
(?: # name/index/noncap alternation noncap group)
(?<named>\?\< # named ?<name>)
(?<name>[\w][\w\d_]+)