If you want work with a byte to contain your values in the range 0 - 255 then you should use pack rather than just assigning the value. Here's a script that uses subroutines to flip, set or unset bits within a byte, bits range from 7 as most significant to 0 as least. Each routine uses vec to create a mask of the bits to be manipulated and displays the mask to show what is going on.

use strict;
use warnings;

use feature qw{say};

my $base = 128;
say q{Non-packed base  - }, unpack q{B*}, $base;
say q{};

$base = pack q{C}, 128;
say q{Packed base      - }, unpack q{B*}, $base;
my $three = pack q{C}, 3;
say q{Three for or     - }, unpack q{B*}, $three;
$base |= $three;
say q{Base now         - }, unpack q{B*}, $base;
say q{};

$base = pack q{C}, 138;
say q{Revised base 138 - }, unpack q{B*}, $base;
flipBits( \ $base, 0 .. 2 );
say q{Flipped base 141 - }, unpack q{B*}, $base;
say q{};

unsetBits( \ $base, 0 .. 7 );
say q{Cleared base     - }, unpack q{B*}, $base;
say q{};

setBits( \ $base, 7 );
say q{Set high bit     - }, unpack q{B*}, $base;
say q{};

setBits( \ $base, 0, 1 );
say q{Set two lowest   - }, unpack q{B*}, $base;
say q{};

flipBits( \ $base, 0 .. 3 );
say q{Flip four lowest - }, unpack q{B*}, $base;
say q{};

setBits( \ $base, 0 .. 2 );
say q{Set three lowest - }, unpack q{B*}, $base;
say q{};

sub flipBits
{
    my( $rsByte, @bits ) = @_;
    my $vec;
    vec( $vec, $_, 1 ) = 1 for @bits;
    say q{Flip mask        - }, unpack q{B*}, $vec;
    ${ $rsByte } = ${ $rsByte } ^ $vec;
}

sub setBits
{
    my( $rsByte, @bits ) = @_;
    my $vec;
    vec( $vec, $_, 1 ) = 1 for @bits;
    say q{Set mask         - }, unpack q{B*}, $vec;
    ${ $rsByte } = ${ $rsByte } | $vec;
}


sub unsetBits
{
    my( $rsByte, @bits ) = @_;
    my $vec;
    vec( $vec, $_, 1 ) = 1 for @bits;
    say q{Unset mask       - }, unpack q{B*}, $vec;
    ${ $rsByte } = ${ $rsByte } &  ( ~ $vec );
}

[download]

The output.

Non-packed base  - 001100010011001000111000

Packed base      - 10000000
Three for or     - 00000011
Base now         - 10000011

Revised base 138 - 10001010
Flip mask        - 00000111
Flipped base 141 - 10001101

Unset mask       - 11111111
Cleared base     - 00000000

Set mask         - 10000000
Set high bit     - 10000000

Set mask         - 00000011
Set two lowest   - 10000011

Flip mask        - 00001111
Flip four lowest - 10001100

Set mask         - 00000111
Set three lowest - 10001111

[download]

I hope this is helpful.

Cheers,

JohnGG

In reply to Re: Modifying multiple bits in a byte - bitwise operators by johngg
in thread Modifying multiple bits in a byte - bitwise operators by stevieb

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