As grep says, you are printing everything, but there are no newlines in any of those variables since split removes them. The output variables overwrite each other because each ends in a carriage return character (this can often be seen in the output as the one line you do get sometimes has garbage at the end left over from previous lines). One solution which builds on grep's and adds a somewhat simpler print statement follows:

my @lines = map{"$_\n"} split /\r\n/, $plain_text;
print @lines[10,11,13,17,18,20];
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If you want to keep the meanings of the various line numbers intact in the code, but avoid creating independent variables for that purpose, you could do something like the following:

use strict;
use LWP::Simple;

my %info_lines = ( title       => 10,
                   timestamp   => 11,
                   shoppers    => 13,
                   num_orders  => 17,
                   gross_sales => 18,
                   avg_size    => 20,
                 );

my $url = "http://www.visionforum.com/admin/avantgo.asp";
my $page_content = get($url);

(my $plain_text = $page_content) =~ s/<[^>]*>//gs;

my @lines = map{"$_\n"} split /\r\n/, $plain_text;
print $lines[$_] for sort values %info_lines;
[download]

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I'd like to be able to assign to an luser