From perlop:

The following escape sequences are available in constructs that interpolate and in transliterations.

...
    \033    octal char    (ESC)
    \x1b    hex char    (ESC)
    \x{263a}    wide hex char    (SMILEY)
    \c[        control char    (ESC)
    \N{name}    named Unicode character
[download]

So

from => "\x9f",
to => "\x{178}"
[download]

may be what you want. Though it looks like you have some encoding issues to think about too.