DB<31>  (my $x="{{abc}}") =~ s/{{/[[/g; print $x

Unescaped left brace in regex is deprecated, passed through in regex; marked by <-- HERE in m/{{ <-- HERE / at (eval 40)[c:/Perl_524/lib/perl5db.pl:737] line 2.                                                                                 at (eval 40)[c:/Perl_524/lib/perl5db.pl:737] line 2.                                   eval 'no strict; ($@, $!, $^E, $,, $/, $\\, $^W) = @DB::saved;package main; $^D = $^D | $DB::db_stop;                                                   (my $x="{{abc}}") =~ s/{{/[[/g; print $x;                                       ' called at c:/Perl_524/lib/perl5db.pl line 737                                         DB::eval called at c:/Perl_524/lib/perl5db.pl line 3131                         DB::DB called at -e line 1                                              [[abc}}                                                                                                                                                           

  DB<32>  (my $x="{{abc}}") =~ s/{\{/[[/g; print $x                             [[abc}}