my $crypted ;
{
  my $checker = My::Password::Checker->new() ;
  my $password = <STDIN> ;
  chomp $password ;
  die "too short!" unless length $password < 4 ;
  die "too obvious" if $checker->check_obvious($password) ;
  # other tests go here...

  my $salt = generate_random_salt() ;
  $crypted = crypt($password,$salt) ;
}

# $password, $salt, $checker and any other variable
# declared by my inside the block disappear here :-)
# $crypted was declared outside the block, so I can...
do_whatever_with($crypted) ;