1. if usage of $a |= 0x00000008; is right ?
Yes. All you have to do is try it: 
use strict; 
use warnings; 

my $val = 0xffff_fff0;
printf "%x\n", $val;
$val |= 0x0000_0008;
printf "%x\n", $val;

__END__

fffffff0
fffffff8

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Side note: don't use $a as a variable name as it has special significance in Perl (sort).
2. how extract hex value by Regular Expression from string I have : For example:

You can use the [[:xdigit:]] character class to extract hex values. See perlre.

In reply to Re: Bit operation by toolic
in thread Bit operation by toren

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