OK. Seems you are right! Thanks! BTW I tried to reproduce it on FreeBSD system with non-Unicode locale (i.e. console, locale and filenames are in KOI8-R). But seems it works fine (perl 12) and escapes characters (while escape are wrong):

"\x{00d5}" does not map to koi8-r at \x{0552}\x{006f}33.pl line 18.
"\x{00d2}" does not map to koi8-r at \x{0552}\x{006f}33.pl line 18.
"\x{00c1}" does not map to koi8-r at \x{0552}\x{006f}33.pl line 18.

...

Died at \x{0552}\x{006f}33.pl line 28.
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While linux (perl 10 and perl 14) does not try to escape (probably detects UTF8 locale)