Extending this logic a bit, and using <DATA> to read in the test data:

use strict;
use warnings;
my ($first_line, $current_line);
while (<DATA>) {    
    chomp; # get rid of newline
    # get the first line sorted
    if ($. == 1) {
        $first_line = join ",", sort( split /,/,);    
    } else { #die if doesn't match the first line sorted.
        $current_line = join ",", sort( split /,/,);
        die "$_ didn't match first line" unless $current_line eq $firs
+t_line;
    }


}
__DATA__
~cake,pastry,donuts,meringue
pastry,~cake,meringue,donuts
meringue,
donuts,pastry,~cake,meringue
[download]

This dies on the third line, as it should.