G'day fishy,

I work with biological data that's often of comparable size — I have a 2GB CSV file that I use for volume testing. I would never attempt to slurp an entire file of this size; instead, I would read and process line-by-line. Apart from the huge memory overhead, you're reading the data twice: once to slurp; again to process.

I don't have Raku available. Here's a quick-and-dirty example in Perl5. I've mostly used the same variable names as your code; hopefully, a conversion to Raku would not be too difficult for you.

Input CSV:

$ cat dummy.csv
a,b,c
d,e,f
g,h,i
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Perl5 script column_extract.pl:

#!/usr/bin/env perl

use strict;
use warnings;
use autodie;
use constant TARGET_COL => 1;

use Text::CSV;

my $file_name = 'dummy.csv';
my @columns;
my $csv = Text::CSV::->new();
open my $fh, '<', $file_name;

while (my $row = $csv->getline($fh)) {
    push @columns, $row->[TARGET_COL];
}

print "@columns\n";
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Output:

$ ./column_extract.pl
b e h
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