Dear Monks, My gods are in disagreement, who can I trust? The Encode page http://perldoc.perl.org/Encode.html#The-UTF8-flag says: 
After $utf8 = decode('foo', $octet); ,

  When $octet is...   The UTF8 flag in $utf8 is
  ---------------------------------------------
  In ASCII only (or EBCDIC only)            OFF
  In ISO-8859-1                              ON
  In any other Encoding                      ON
  ---------------------------------------------

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Yet at the altar of Perl 5.10.0 and Perl 5.8: 
#use utf8;
#use encoding 'iso-8859-1';
#use encoding 'utf-8-strict';
#use encoding::warnings;  #check for implicit upgrade
use Encode;

print '${^UNICODE}='.${^UNICODE}."\n\n";

$a = "face";
$b = "not_a_face=\x{e2}\x{98}\x{ba}";
print "a=",Encode::is_utf8($a)," b=",Encode::is_utf8($b),"\n\n";

$a=Encode::decode('iso-8859-1',$a);
$b=Encode::decode('iso-8859-1',$b);
print "a=",Encode::is_utf8($a)," b=",Encode::is_utf8($b),"\n\n";

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Produces: 
${^UNICODE}=63
a= b=
a=1 b=1

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Showing that a pure ASCII string has the utf8 flag set. My faith in Perl Unicode is tested. Monks can you help me see the light?

Bryce Nesbitt, Berkeley Electronic Press, Berkeley CA

In reply to Why is utf8 flag set after Encode::decode of pure ASCII? by brycen

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