It's hard for me to tell what your problem might be, since the code you posted looks incomplete. I highly recommend using the following at the top of your script.

use strict;
use warnings;
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The warning or errors you get will give you clues how to fix your code.

Here is working code for printing out the first three columns of a test.csv file.

#!/usr/bin/env perl
use strict;
use warnings;
use Text::CSV;

my @c1 = column_segregation(0);
print join(", ", @c1), "\n";
my @c2 = column_segregation(1);
print join(", ", @c2), "\n";
my @c3 = column_segregation(2);
print join(", ", @c3), "\n";

exit;

sub column_segregation
{
    my $o = $_[0];
    my @array_A2;
    
    my $csv = Text::CSV->new ({ binary => 1 });
    open (my $io, "<", "test.csv") or die "Could not open test.csv";
    while (my $row = $csv->getline($io)) {
        push @array_A2, $row->[$o];
    }
   return (@array_A2);                                     
}
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