Hmm... Not sure why you'd want this, but anyway. Here's a one-liner that does it, but broken out for clarity:

while (<>)
{
    s|"([^"]+)"|
        '{' .
         join(',',
             map { "(byte)'$_'" }
                 split(//, $1)
             ) .
         '}'
      |gex;
    print;
}
[download]

Main difference is that this will match many quoted strings on a line. Like your example, it won't cope with "escaped \" quotes".

HTH