>perl -wMstrict -le
"my $s =
   '<a>foo</a><bc>bar</bc> <def>baz</def> \"x\" <ghij>%&*</ghij>';
 print qq{'$s'};
 ;;
 $s =~ s{ < ([^>]+) > ((?: (?! </ \1) .)*) </ \1 > }{$2}xmsg;
 print qq{'$s'};
 ;;
 ;;
 $s = '<B>foo</ b > <efg>bar</efg> \"stuff\" <cD >*&!</ Cd>';
 print qq{'$s'};
 ;;
 my @tags = qw(b cd);
 my $tag  = join '|', @tags;
    $tag  = qr{ (?i) $tag }xms;
 use re 'eval';
 $s =~ s{ < \s* ($tag) \s*  >
          ((?: (?! </ \s* \1) .)*)
          </ \s* ([^>]*) (?(?{ lc($1) ne lc($^N) }) (*F)) \s* >
        }
        {$2}xmsg;
 print qq{'$s'};
"
'<a>foo</a><bc>bar</bc> <def>baz</def> "x" <ghij>%&*</ghij>'
'foobar baz "x" %&*'
'<B>foo</ b > <efg>bar</efg> "stuff" <cD >*&!</ Cd>'
'foo <efg>bar</efg> "stuff" *&!'