$ cat text_ob.pl
#!/usr/bin/perl -w

use strict;

my $randChar = sub () {
        return  chr(int(rand(26)) + 65);
};

while (<DATA>) {
        #s/(\w)/(??{$randChar->()}/g;
        s/(\w)/$randChar/g;
        print $_;
}
__DATA__
ABCDEFG

$ ./text_ob.pl
CODE(0x1014078c)CODE(0x1014078c)CODE(0x1014078c)CODE(0x1014078c)CODE(0x1014078c)CODE(0x1014078c)CODE(0x1014078c)

##</code><code>##

HJAxQPv