Leo_Yao has asked for the wisdom of the Perl Monks concerning the following question:

I try to use utf8::upgrade to upgrade a variable, but when I use print to see what happened to the variable, I found nothing was changed. 

$s=chr(192);
printf "%vd\n", $s;
utf8::upgrade($s);
printf "%vd\n", $s;

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But if I use "use bytes", the value of $s is changed. Why is it?

use bytes;

$s=chr(192);
printf "%vd\n", $s;
utf8::upgrade($s);
printf "%vd\n", $s;

[download]

Replies are listed 'Best First'.
Re: Does the utf8::upgrade change the value?
by Anonymous Monk on Feb 25, 2011 at 12:21 UTC
    Because that is how utf8::upgrade works, if there is nothing to change, it doesn't change anything
[reply]

      Thanks. But I still don't understand why the value is changed in the case of "use bytes".

[reply]
        character semantics 
        $ perl -MDevel::Peek -e "Dump $f=chr(400) "
SV = PV(0x3e69ec) at 0x98a414
  REFCNT = 1
  FLAGS = (POK,pPOK,UTF8)
  PV = 0x98419c "\306\220"\0 [UTF8 "\x{190}"]
  CUR = 2
  LEN = 4

        [download]
        byte semantics 
        $ perl -MDevel::Peek -e " use bytes; Dump $f=chr(400) "
SV = PV(0x3e69f4) at 0x98a434
  REFCNT = 1
  FLAGS = (POK,pPOK)
  PV = 0x9841ac "\220"\0
  CUR = 1
  LEN = 4

        [download]
        utf8::upgrade makes character semantics again 
        $ perl -MDevel::Peek -e " use bytes;  $f=chr(400); utf8::upgrade($f); 
+Dump $f "
SV = PV(0x3e6a0c) at 0x98a474
  REFCNT = 1
  FLAGS = (POK,pPOK,UTF8)
  PV = 0x3ef4e4 "\302\220"\0 [UTF8 "\x{90}"]
  CUR = 2
  LEN = 3

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        bytes
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