use strict;
use warnings;
use Data::Dumper;

my @list1 = qw(a b c);
my @list2 = qw(d e f);

changem([@list1], [@list2]);

print "\n=== After changem ===\n";
printf "%s\n", join q(, ), @list1;
printf "%s\n", join q(, ), @list2;

sub changem {
    my $aref1 = shift or die "no list1";
    my $aref2 = shift or die "no list2";

    $aref1->[1] = 'Camel';
    $aref2->[1] = 'LLama';

    print "list1: " . Dumper($aref1);
    print "list2: " . Dumper($aref2);
}

##</code><code>##

list1: $VAR1 = [
          'a',
          'Camel',
          'c'
        ];
list2: $VAR1 = [
          'd',
          'LLama',
          'f'
        ];

=== After changem ===
a, b, c
d, e, f

##</code><code>##

use strict;
use warnings;

my @a1 = qw(keats byron frost);
my @a2 = qw(marlowe shakespeare jonson);

handle_two( \@a1, \@a2 );
exit(0);


sub handle_two {
    my ($aref1, $aref2) = @_;

    for my $aref ($aref1, $aref2) {
        do_something_with_one( $aref );
    }
    return;
}

sub do_something_with_one {
    my ($aref) = @_;
    printf "%s\n", join q(, ), @$aref;
    return;
}

__END__

##</code><code>##

keats, byron, frost
marlowe, shakespeare, jonson

##</code><code>##

use strict;
use warnings;
use Data::Dumper;

my @list1 = qw(a b c);
my @list2 = qw(d e f);

changem(\@list1, \@list2);

print "\n=== After changem ===\n";
printf "%s\n", join q(, ), @list1;
printf "%s\n", join q(, ), @list2;

sub changem {
    my $aref1 = shift or die "no list1";
    my $aref2 = shift or die "no list2";

    $aref1->[1] = 'Camel';
    $aref2->[1] = 'LLama';

    print "list1: " . Dumper($aref1);
    print "list2: " . Dumper($aref2);
}

##</code><code>##

list1: $VAR1 = [
          'a',
          'Camel',
          'c'
        ];
list2: $VAR1 = [
          'd',
          'LLama',
          'f'
        ];

=== After changem ===
a, Camel, c
d, LLama, f