$_ = "This line contains 0xC30x86n exotic character.";
s/0x([0-9a-fA-F]{2})/chr(hex($1))/eg;
utf8::decode($_);
[download]

You could create an HTML from that string as follows:

use HTML::Entities qw( encode_entities );
open(my $fh, '>:encoding(UTF-8)', 'file.html') or die;
print $fh qq{<meta http-equiv="Content-Type" content="text/html; chars
+et=UTF-8">\n};
print $fh qq{<title>Test</title>\n};
print $fh encode_entities($_);   # Escapes &<>'"
[download]

The file will contain

3C 6D 65 74 61 20 68 74-74 70 2D 65 71 75 69 76   <meta http-equiv
3D 22 43 6F 6E 74 65 6E-74 2D 54 79 70 65 22 20   ="Content-Type"
63 6F 6E 74 65 6E 74 3D-22 74 65 78 74 2F 68 74   content="text/ht
6D 6C 3B 20 63 68 61 72-73 65 74 3D 55 54 46 2D   ml; charset=UTF-
38 22 3E 0D 0A 3C 74 69-74 6C 65 3E 54 65 73 74   8">..<title>Test
3C 2F 74 69 74 6C 65 3E-0D 0A 54 68 69 73 20 6C   </title>..This l
69 6E 65 20 63 6F 6E 74-61 69 6E 73 20 26 41 45   ine contains &AE
6C 69 67 3B 6E 20 65 78-6F 74 69 63 20 63 68 61   lig;n exotic cha
72 61 63 74 65 72 2E                              racter.
[download]

The HTML reader will render it as

This line contains Æn exotic character.