I'm not sure why chromatic seemed to miss the boat on this one. Although I might be wrong, it would seem that the linefeed ("\n") is being left on the fourth element of the array. Maybe a rushed posting. Here's a more compacted version:

my @output = sort { $a->[0] cmp $b->[0]
                 || $a->[3] <=> $b->[3] }
             map { chomp; [ split(',', $_, 4) ] }
             <INPUT_FILE>;
[download]

Remember that with this kind of structure the data flows from the bottom up. From the file, through the map which makes the proper array-of-arrays (AoA), and in to the sort routine which re-orders it before storing the result in @output.

As a note, though, comparing phone numbers numerically is pretty lacking. If one has a dot and the other a dash, your sort is going to be ruined. Here's a more robust version that only sorts the numerical component of the phone number, ignoring brackets, dashes and the like:

sub phone_value
{
     my ($v) = @_;
     $v =~ tr/^0-9//d;
     return $v;
}

my @output = sort { $a->[0] cmp $b->[0]
                 || phone_value($a->[3]) <=> phone_value($b->[3]) }
             map { chomp; [ split(',', $_, 4) ] }
             <INPUT_FILE>;
[download]