#! /usr/bin/env perl
use strict;
use warnings;
use 5.010.000;

#> sub routines
#> --------------------------------------------------------------------------

sub hexstring_bitwise_reverted {
    # see output of "perldoc -f convert"; or see manually in perlfaq4
    return sprintf "0x%02X", oct( "0b" . reverse sprintf( "%08b", oct(shift) ) );
#          |                 |           |       |                |   |
#          |                 |           |       |                |   fetch first argument (a hex string 0xAB)
#          |                 |           |       |                convert it to decimal
#          |                 |           |       create bitstring of decimal
#          |                 |           invert the order of the bits in bitstring
#          |                 convert reverted bitstring back to decimal
#          create a hexstring again to return
}


#> main program
#> --------------------------------------------------------------------------


my $hexstring = "0xFC";

say join "\n", $hexstring, hexstring_bitwise_reverted( $hexstring );