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
[download]

As you can see, no difference between the two forms