DB<3> if ( $str =~ /(\\x{[A-F\d]+})/i ) { print $1 }                          
Unescaped left brace in regex is deprecated here (and will be fatal in Perl 5.30), passed through in regex; marked by <-- HERE in m/(\\x{ <-- HERE [A-F\d]+})/ at (eval 13)[/usr/share/perl/5.28/perl5db.pl:738] line 2.