my $hex= "FFAA";
my $signed= unpack "s", pack "S", unpack "v", pack "H*", $hex;

##</code><code>##

my $hex= "ABC";
my $unsigned= unpack "V", pack "h*", "".reverse "00000000".$hex;
my $signed= unpack "l", pack "L", unpack "V", pack "h*",
    "".reverse(  ( $hex=~/^[89a-f]/i ? "F" : "0" ) x 8 . $hex  );