>perl -wMstrict -le
"my $s =
   '<B>foo</ b > <EfG>bar</eFg> \"stuff\" <cD >*&!</ Cd> <x>baz</x>';
 print qq{'$s'};
 ;;
 my $ar_tag_delete_content = [ 1, tag_group_regex(qw(efg) ) ];
 my $ar_tag_leave_content  = [ 0, tag_group_regex(qw(b cd)) ];
 ;;
 for my $pass ($ar_tag_leave_content, $ar_tag_delete_content) {
   my ($delete_content, $tag) = @$pass;
   use re 'eval';
   $s =~ s{ < \s* ($tag) \s*  >
            ((?: (?! </ \s* \1) .)*)
            </ \s* ([^>]*) (?(?{ lc($1) ne lc($^N) }) (*F)) \s* >
          }
          { $delete_content ? '' : $2 }xmsge;
   print qq{'$s'};
   }
 ;;
 sub tag_group_regex {
   my $alternation = join '|', @_;
   return qr{ (?i) $alternation }xms;
   }
"
'<B>foo</ b > <EfG>bar</eFg> "stuff" <cD >*&!</ Cd> <x>baz</x>'
'foo <EfG>bar</eFg> "stuff" *&! <x>baz</x>'
'foo  "stuff" *&! <x>baz</x>'