sub markets {
   my $self = shift;
   $self->_fetch_markets();
   $self->_parse_markets();
   return $self->{markets};
}

sub _fetch_markets {
   my $self = shift;
   return if $self->{markets_raw};
   # code hier, um $self->{markets_raw} zu befüllen
   ...
}

sub _parse_markets {
    my $self = shift;
    return if $self->{markets};
    $self->{markets} = decode_json $self->{markets_raw};
}