How can I reverse the bits of an unsigned byte in Perl?

For example, the number 178 should convert to the letter "M".

178 is 10110010.

Reversing all of the bits should give 01001101, which is 77 or "M" as a character. I taught about using the Reverse function but I don't know how can I use it on an @array.

use strict;
use warnings 'all';

    open(my $fh1, '<', 'sym.dat') or die $!;
    open(my $fh2, '<', 'sym2.txt') or die $!;
    open my $fh_out, '>', 'symout.txt' or die $!;

    until ( eof $fh1 or eof $fh2 ) {

        my @l1 = map hex, split '', <$fh1>;
        my @l2 = map hex, split '', <$fh2>;
        my $n = @l2 > @l1 ? @l2 : @l1;

        my @sum = map {
            no warnings 'uninitialized';
        $l1[$_] + $l2[$_];
    } 0 .. $n-1;
        @sum = map { split //, sprintf '%08X', $_ } @sum;
        print { $fh_out } "reverse @sum\n";
    }

I am calculating here the sum of hex values but the question is the same I want to reverse the byte values.

You call reverse() on an array, by just passing the array to the function. However, like all Perl functions, you can't put a function call inside a string. So instead of

print { $fh_out } "reverse @sum\n";

You want:

print { $fh_out } reverse(@sum), "\n";

The parentheses around @sum are required here to prevent the newline from being included in the arguments to reverse.