I got the following results with perl v5.14.2:
my $string="1234567812345678";
print join("_", unpack("H32V*", $string)),"\n";
my @temp = unpack("H32V*", $string); print join("_", @temp),"\n";
$string="12345678123456781111";
print join("_", unpack("H32V*", $string)),"\n";
@temp = unpack("H32V*", $string); print join("_", @temp),"\n";
#prints:
31323348355037383132333435363738
31323348355037383132333435363738
31323334353637383132333435363738_825307441
31323334353637383132333435363738_825307441
As you can see, no difference between the two forms