sub new {
  my $class = shift;
  my $self = {};
  $self->{atr1} = undef;
  $self->{atr2} = undef;
  # more attributes...
  bless($self, $class);
  # ... some code to populate attribs from passed parms
  return $self;
}

##</code><code>##

use MyMod;
my $mm = MyMod->new(atr1 => 1, atr2 => 'string2');