Use of uninitialized value $+{"intern"} in regexp compilation at a.pl line 6.

##</code><code>##

(?x-ism:
(?<intern>
 \<
 (?:
  [^<>]++
  |
  (?)
 )*+
 \>
)
)

##</code><code>##

(?$+{intern})

##</code><code>##

(?&intern)