# check 'name' entry
unless ($name) {
  $this->stash->{exception} .= "bad name\n";
}

# check 'address' entry
unless ($address) {
  $this->stash->{exception} .= "bad address\n";
}

# check 'phone' entry
unless ($phone) {
  $this->stash->{exception} .= "bad phone\n";
}

return $this->error( $this->stash->{exception} ) 
  if $this->stash->{exception};

...