Best How To :

Unless your data includes quoted fields, like a,b,c,"complicated field, quoted",e,f,g there is no advantage in using Text::CSV over a simple split /,/.

This example categorizes the data into a hash that you can access simply and directly. I have used Data::Dump only to show the contents of the resulting data structure.

use strict;
use warnings;
use autodie;

open my $fh, '<', 'mydata.csv';

my $category;
my %data;
while (<$fh>) {
  chomp;
  my @data = split /,/;
  my $cat = shift @data;
  $category = $cat if $cat =~ /\S/;
  push @{ $data{$category} }, \@data;
}

use Data::Dumper;
$Data::Dumper::Useqq = 1;
print Dumper \%data;

output

{
  "Category 1" => [
                    [" header1", " header2", " header3", "..."],
                    [" data", " data", " data", "..."],
                    [" data", " data", " data", "..."],
                    [" data", " data", " data", "..."],
                  ],
  "Category 2" => [
                    [" header1", " header2", " header3", "..."],
                    [" data", " data", " data", "..."],
                    [" data", " data", " data", "..."],
                    [" data", " data", " data", "..."],
                  ],
  "Category 3" => [
                    [" header1", " header2", " header3", "..."],
                    [" data", " data", " data", "..."],
                    [" data", " data", " data", "..."],
                    [" data", " data", " data", "..."],
                  ],
}

Update

If all you want is to separate a given section of the file then there is no need to put it into a hash. This program will do what you want.

#!/usr/bin/perl

use strict;
use warnings;
use autodie;

my ($file, $wanted) = @ARGV;

open my $fh, '<', $file;

my $category;

while (<$fh>) {
  my ($cat) = /\A([^,]*)/;
  $category = $cat if $cat =~ /\S/;
  print if $category eq $wanted;
}

Run it like this on the command line

get_category.pl mydata.csv 'Category 2' > cat2.csv

output

Category 2, header1, header2, header3,...,
          , data, data, data,...,
          , data, data, data,...,
          , data, data, data,...