Show us some code that demonstrates the problem. Corion has shown various sample code that probably answers your question, but I suspect you don't understand it so you are guessing at answers and are not only getting it wrong, but you are probably providing misleading information to us too.
So, show us some sample code using one of the two strings "\x0D\x0E\x0A\x0D\x0B\x0E\x0E\x0F" or "\xDE\xAD\xBE\xEF" (whichever is appropriate) and tell us what you get and what you expect. Note that the second string is most likely to be correct. Both strings are big endien.
For your original question the code is simply my $flags = unpack('N', "\0\0\0\x01");
True laziness is hard work