The problem is that you need to get 
my $regex2 = qr% \n
   (?:
      \QI'll be good.\E
      | Hushing
      | Hrumph
      | \Q>:[\E | \Q:-(\E | \Q:(\E | \Q:-c\E | \Q:c\E | \Q:-<\E | \Q:<
+\E
      | \Q:-[\E | \Q:[\E  | :\{ | \Q:-|\E | \Q:@\E | \Q>:(\E | \Q:'-(\
+E
      | \Q:'(\E
      | \QShutting up now.\E
      | \QBut, but...\E
      | \QI'll be quiet.\E
   )
%mix;

[download]

But, as curly braces are the delimiters, qr{ \{ } turns into qr% { %', , but there's no way how to express 'qr% \{ % with curlies as the delimiters - but you don't need that, as they're equivalent.

That's why I don't like using curlies as regex delimiters.

#!/usr/bin/perl
use warnings;
use strict;
use feature qw{ say };

my @res = ( qr% a{1 %,
            qr{ a\{1 },
            qr% a\{1 %,
            qr% a\Q{\E1 %,
            qr{ a\Q\{\E1 },

            qr% a{{1}1 %,
            qr{ a\{{1}1 },
            qr{ a\{{1}1 },
            qr{ a\{\{1\}1 },
            qr% a\{{1}1 %,

          );

say $_, ' a{1 ' =~ $_ for @res;

[download]

Update: more examples in the second code.

($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,

[download]

In reply to Re: Regex Search pattern not terminated error by choroba
in thread Regex Search pattern not terminated error by neilwatson

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