$ perl -we'$x = v255;
 {use bytes; print STDERR "len:",($len=length $x),"\n" }
 print STDERR "wrote: ",($x = syswrite STDOUT, $x, $len),"\n"'|cat
len:2
wrote: 1
˙

$ perl -we'$x = "\xff";
 {use bytes; print STDERR "len:",($len=length $x),"\n" }
 print STDERR "wrote: ",($x = syswrite STDOUT, $x, $len),"\n"'|cat
len:1
wrote: 1
˙

$ perl -CO -we'$x="\xff";
 {use bytes;print STDERR "len:",($ln=length $x),"\n"  }
 print STDERR "wrote: ",($x = syswrite STDOUT, $x, $len),"\n"'|cat
len:1
wrote: 1
Aż

$ perl -CO -we'$x=v255;
 {use bytes; print STDERR "len:",($len=length $x),"\n" }
 print STDERR "wrote: ",($x = syswrite STDOUT, $x, $len),"\n"'|cat
len:2
wrote: 1
Aż