my ($command1, $command2, $command3) = @ARGV;
$command2 = 'default' unless defined $command2;
$command3 = 'hoo hah' unless defined $command3;

# OR

my $command1 = shift or die; # Ideally call a subroutine to print usage and die
my $command2 = shift || 'default';
my $command3 = shift || 'hoo hah';

##</code><code>##

my $command1 = <STDIN>; chomp($command1);
my ($command2, $command3) = ('default', 'hoo hah');
unless (eof(STDIN)) {
    $command2 = <STDIN>; chomp $command2;

    unless (eof(STDIN)) {
        $command3 = <STDIN>; chomp $command3;
    }
}