Hello rahularora, and welcome to the Monastery!

Here is one way:

#! perl
use strict;
use warnings;

my @fields = (42, undef, 'abc', undef, 'foo', 'bar');
my $flags  = 0;
my $mask   = 0b1000_0000;

for my $field (@fields)
{
    $flags |= $mask if defined $field;
    $mask >>= 1;
}

printf "%08b\n", $flags;
[download]

Output:

13:35 >perl 640_SoPW.pl
10101100

13:36 >
[download]

See Bitwise String Operators and Shift Operators.

Hope that helps,