package Foo;

sub new {
  my $class = shift;
  my %self = @_;

  return bless \%self, $class;
}

sub do_something {
  my $self = shift;

  print "msg is: ", $self->{msg}, "\n";
}

## Meanwhile, back on the ranch . . . erm, in the main package
package main;

my $foo = Foo->new( msg => "WUBBA WUBBA" );

$foo->do-something;