s/(\d\d)/chr(0x80+$1)/ge;

##</code><code>##

$_="00 01 98 99";
s/(\d\d)/chr(0x80 + $1)/ge;
@f= map {sprintf "%x", $_} unpack("C*", $_);
print "@f\n";

##</code><code>##

80 20 81 20 e2 20 e3