See the current Perl documentation for hex.

Here is our local, out-dated (pre-5.6) version:

hex - convert a string to a hexadecimal number

hex EXPR


Interprets EXPR as a hex string and returns the corresponding value. (To convert strings that might start with either 0 or 0x see oct.) If EXPR is omitted, uses $_.

    print hex '0xAf'; # prints '175'
    print hex 'aF';   # same