slothbear:~/perltest marvin$ cat BackslashX.pm 
package BackslashX;
use strict;
use warnings;

use Encode '_utf8_on';

our $smiley = "\xE2\x98\xBA";
_utf8_on($smiley);

1;

slothbear:~/perltest marvin$ cat backslash_x.plx 
#!/usr/bin/perl
use strict;
use warnings;

use encoding 'iso-8859-1';
use BackslashX;
use Devel::Peek;

Dump($BackslashX::smiley);
print $BackslashX::smiley;
print "\n";

slothbear:~/perltest marvin$ perl backslash_x.plx 
SV = PV(0x1834224) at 0x181ed98
  REFCNT = 1
  FLAGS = (POK,pPOK,UTF8)
  PV = 0x372010 "\342\230\272"\0 [UTF8 "\x{263a}"]
  CUR = 3
  LEN = 4
"\x{263a}" does not map to iso-8859-1 at backslash_x.plx line 11.
\x{263a}