Another approach to this is to use a Schwartzian Transform. Here's an example using this approach. Note that the split used here has the advantage of working on people with middle initials, and those with only a one word name. The trinary in the top map is also to deal with those with only a single name.

#!/usr/bin/perl

use warnings;
use strict;

# Note: Read a Schwartzian transform from
#  the bottom-up.  It makes more sense.
my @names =
  # Join the name back together.  First name
  #  output first, and then (And only if a
  #  surname exists) a comma followed by the
  #  surname.
  map {$_->[1]. ($_->[0]?", $_->[0]":'')}
  
  # Sort the arrays by lastname.
  sort {$a->[1] cmp $b->[1]}
  
  # Splits the name on the final spaces, creates
  #  arrays with [firstname, lastname].
  map {/(.*?)\s*(\S+)$/; [$1,$2]}

  # All of the output
  <>;

print "'$_'\n" foreach @names;
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