$decimal = sprintf "%d", $num; # or trivially removed, since automatic
$octal = sprintf "%o", $num;
$hex = sprintf "%h", $num;
$binary = sprintf "%b", $num; # 5.6 only
$num = 0+ $decimal; # or trivially removed, since automatic
$num = oct($octal);
$num = unpack "N", pack "H*", $hex;
$num = unpack "N", pack "B*", $binary;