$attrs{'error'}         = 'cancel-url and success-url cannot be derived from the environment and need to be provided' unless ($attrs{'cancel-url'} and $attrs{'success-url'});

    $attrs{'error'} = 'Public API key provided is not a valid key' if $attrs{'api-public'} and $attrs{'api-public'} !~ /^pk_/;
    $attrs{'error'} = 'Secret API key provided is not a valid key' unless $attrs{'api-secret'} =~ /^sk_/;
    $attrs{'error'} = 'Secret API key provided as Public key' if $attrs{'api-public'} and $attrs{'api-public'} =~ /^sk_/;
    $attrs{'error'} = 'Public API key provided as Secret key' if $attrs{'api-secret'} =~ /^pk_/;
    $attrs{'error'} = 'Secret API key is too short' unless length $attrs{'api-secret'} > 100;
    $attrs{'error'} = 'Secret API key is missing' unless $attrs{'api-secret'};
    
    return bless \%attrs, $class;