For production use, you might as well use Sort::Fields or Text::CSV as pointed out by merlyn.

But if your purpose is learning, apart from the other solutions mentioned in this thread, you may want to take a look at the following. The line with the assignment to @sorted_lines is called a Schwartzian Transform and is named after its inventor, merlyn himself. For good discussions and descriptions of how this works, see:

• Schwartzian Transform (merlyn)
• Schwartzian Transform (chromatic)
• Schwartzian Transform vs. plain Perl
• How do I sort an array by (anything)?
• Complex sorting

And the code is:

#!/usr/local/bin/perl -w

use strict;
use vars qw($field @lines @sorted_lines);

$field=shift @ARGV;

@lines=<>;

# This is the Schwartzian transform
@sorted_lines=
        map { $_->[0] }
        sort { $a->[1] cmp $b->[1] }
        map { [$_, (split(/,\s*/, $_))[$field] ] }
        @lines;

print @sorted_lines;
[download]

Once you fully understand the Schwartzian Transform, you'll be on your way to enlightenment :-)

--ZZamboni