(
                     (       (
                           (         (
                (    (         (            (
                                       (
             (      (       (    (          (    (
                             ''
                )      )      )))   )    )     )   )
           )                  )))))
                  )          =~("\(".           (
                       (    '?')).'{'   .    (
                (           '`')|'%')
                             .('['^  (   '-')
                      )    .    (     '`'|'!')
                                .  ('`'|"\,").
                             '"'.('['^"\+").(
                        '['^')').('`'|(')')).(
                    '`'|'.').('['^'/').(('{')^
                    '[').'\\'.'"'.('`'|"\(").(
                    '`'|'%').('`'|',').("\`"|
                    ',').('`'|'/').('{'^'[').
                    ('['^',').('`'|'/').("\["^
                   ')').('`'|',').('`'|('$')).
                  '\\'.'\\'.('`'|'.').'\\'.'"'
                  .';'.('!'^'+').'"'.'}'.')');

##</code><code>##

Eval-group not allowed at runtime, use re 'eval' in regex m/(?{eval"print\"hello world\\n\";
"})/ at v1.pl line 25.

##</code><code>##

perl -MO=Deparse v1.pl

##</code><code>##

'' =~ /(?{eval"print \"hello world\\n\";\n"})/;
v1.pl syntax OK

##</code><code>##

use re 'eval';

##</code><code>##

use if $] >= 5.017, re => 'eval';

##</code><code>##

use if $^V && $^V gt 5.17.0, re => 'eval';