The function sprintf returns a string, and "0x3cb37140" is a string, while the bareword (in code) 0x3cb37140 is not - it is converted to a number. You can convert the string to a number with hex or eval. Also, adding and subtracting 0x1 doesn't give the result you expected:

use Devel::Peek;
my $hex = sprintf( "0x%02x%02x%02x40", 60,179,113 );

print "\n\$hex as returned from sprintf:\n";
Dump($hex);

my $num = hex $hex;
print "\$hex hex()ed:\n";

Dump($num);

$hex += 0x1;

print "\$hex augmented with 0x01:\n";

print $hex,"\n";

__END__

$hex as returned from sprintf:
SV = PV(0x8c90c20) at 0x8c90750
  REFCNT = 1
  FLAGS = (PADBUSY,PADMY,POK,pPOK)
  PV = 0x8cb34f0 "0x3cb37140"\0
  CUR = 10
  LEN = 12
$hex hex()ed:
SV = IV(0x8cabcac) at 0x8c9078c
  REFCNT = 1
  FLAGS = (PADBUSY,PADMY,IOK,pIOK)
  IV = 1018392896
$hex augmented with 0x01:
1
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Strings are stored in a PV (pointer value) slot of a SV (scalar value), while integers get stored in the IV (integer value) slot of an SV. A variable can even carry both representations:

my $hex = sprintf("0x%02x%02x%02x40", 60,179,113);
$hex = hex($hex);
Dump($hex)
__END__
SV = PVIV(0x84d3b10) at 0x84d1cdc
  REFCNT = 1
  FLAGS = (PADBUSY,PADMY,IOK,pIOK)
  IV = 1018392896
  PV = 0x84e5608 "0x3cb37140"\0
  CUR = 10
  LEN = 12
[download]

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