my @data = <$fh>;

##</code><code>##

my $data_ref;
@$data_ref = <$fh>;

##</code><code>##

my $data_ref = [ <$fh> ];

##</code><code>##

$ ls -lSr text_?_1
-rw-r--r--  1 ken  staff        1000  8 Feb  2013 text_K_1
-rw-r--r--  1 ken  staff     1000000  8 Feb  2013 text_M_1
-rw-r--r--  1 ken  staff  1000000000  8 Feb  2013 text_G_1

##</code><code>##

#!/usr/bin/env perl -l

use strict;
use warnings;
use autodie qw{:all};

use Devel::Size qw{size total_size};

{
    open my $fh, '<', $ARGV[0];

    my @data = <$fh>;

    print 'size(\@data):          ', size(\@data);
    print 'total_size(\@data):    ', total_size(\@data);
}

{
    open my $fh, '<', $ARGV[0];

    my $data_ref;
    @$data_ref = <$fh>;

    print 'size($data_ref):       ', size($data_ref);
    print 'total_size($data_ref): ', total_size($data_ref);
}

{
    open my $fh, '<', $ARGV[0];

    my $data_ref = [ <$fh> ];

    print 'size($data_ref):       ', size($data_ref);
    print 'total_size($data_ref): ', total_size($data_ref);
}

##</code><code>##

$ pm_1171361_mem_use_array.pl ~/local/dev/test_data/text_K_1
size(\@data):          144
total_size(\@data):    1494
size($data_ref):       144
total_size($data_ref): 1494
size($data_ref):       144
total_size($data_ref): 1494

##</code><code>##

$ pm_1171361_mem_use_array.pl ~/local/dev/test_data/text_M_1
size(\@data):          80064
total_size(\@data):    1420366
size($data_ref):       80064
total_size($data_ref): 1420366
size($data_ref):       80064
total_size($data_ref): 1420366

##</code><code>##

$ pm_1171361_mem_use_array.pl ~/local/dev/test_data/text_G_1
size(\@data):          80000064
total_size(\@data):    1420322314
size($data_ref):       80000064
total_size($data_ref): 1420322314
size($data_ref):       80000064
total_size($data_ref): 1420322314