use strict;
use warnings;

use Data::Dumper;

my @in = qw(
    john,doe,sam,jr
    albert,simpson
    barry,white,,III
    harry,potter
    steve,zurk,james,sr
);
my @in_split = map { [ split /,/ ] } @in;
my @in_hashed = map {
    {
        fname   => $_->[0],
        lname   => $_->[1],
        mname   => $_->[2],
        surname => $_->[3],
    }
} @in_split;

my @in_sorted = sort {
    (
               defined $a->{mname}
            && defined $b->{mname}
            && (
            lc substr( $a->{mname}, 0, 1 ) cmp lc substr( $b->{mname},
+ 0, 1 )
            )
        )
        || (
        lc substr( $a->{fname}, 1, 1 ) cmp lc substr( $b->{fname}, 1, 
+1 ) )
        || (
        lc substr( $a->{lname}, -1, 1 ) cmp lc substr( $b->{lname}, -1
+, 1 ) )
} @in_hashed;

print Dumper \@in_sorted;
__END__
$VAR1 = [
          {
            'lname' => 'white',
            'mname' => '',
            'fname' => 'barry',
            'surname' => 'III'
          },
          {
            'lname' => 'potter',
            'mname' => undef,
            'fname' => 'harry',
            'surname' => undef
          },
          {
            'lname' => 'simpson',
            'mname' => undef,
            'fname' => 'albert',
            'surname' => undef
          },
          {
            'lname' => 'zurk',
            'mname' => 'james',
            'fname' => 'steve',
            'surname' => 'sr'
          },
          {
            'lname' => 'doe',
            'mname' => 'sam',
            'fname' => 'john',
            'surname' => 'jr'
          }
        ];
[download]

Formatting is by perltidy.

Since some records don't have a middle name, you have to check if that's defined to avoid warnings. In that case, I've skipped comparing on middle name. If you want undef names to sort in a particular place (first or last, I'd guess), then you could code for that.