#!/usr/bin/perl -w
use strict;

my @names = 
 (
     "Builder,Bob",
     "Stein,Franklin",
     "Boop,Elizabeth",
     "Boop,Albert",
     "Bear,Izzy",
     "SomeGuy,Guy",
     "Einstein,Albert",);
   
@names = sort by_last_name @names;

print join("\n",@names),"\n";

sub by_last_name
{
   my ($a_last, $a_first) = split (/,/,$a);
   my ($b_last, $b_first) = split (/,/,$b);
           $a_last cmp $b_last
                   or
           $a_first cmp $b_first        
}

__END__
Prints:
Bear,Izzy
Boop,Albert
Boop,Elizabeth
Builder,Bob
Einstein,Albert
SomeGuy,Guy
Stein,Franklin

##</code><code>##

#!/usr/bin/perl -w
use strict;

my @names = 
 (
     "Builder,Bob",
     "Stein,Franklin",
     "Boop,Elizabeth",
     "Boop,Albert",
     "Bear,Izzy",
     "SomeGuy,Guy",
     "Einstein,Albert",);
   
@names = sort by_last_name @names;

print join("\n",@names),"\n";

## Now print sorted by first name ##

print "\nNow sorted by first name\n";
@names = sort by_first_name @names;

foreach my $full_name (@names)
{
   my ($last,$first) = split (/,/,$full_name);
   print "$first,$last\n";
}

sub by_last_name
{
   my ($a_last, $a_first) = split (/,/,$a);
   my ($b_last, $b_first) = split (/,/,$b);
           $a_last cmp $b_last
                   or
           $a_first cmp $b_first        
}

sub by_first_name
{
   my ($a_last, $a_first) = split (/,/,$a);
   my ($b_last, $b_first) = split (/,/,$b);
           $a_first cmp $b_first
                   or
           $a_last cmp $b_last        
}

__END__
Prints:
Bear,Izzy
Boop,Albert
Boop,Elizabeth
Builder,Bob
Einstein,Albert
SomeGuy,Guy
Stein,Franklin

Now sorted by first name
Albert,Boop
Albert,Einstein
Bob,Builder
Elizabeth,Boop
Franklin,Stein
Guy,SomeGuy
Izzy,Bear