Have a look at this, it may be the sort of thing you are looking for:

package OO;

my $properties = {
    'user' => [ qr/^[a-zA-Z0-9]+$/, 'Username may only contain alphanu
+meric characters' ],
    'password' => [ qr/^[a-zA-Z0-9]+$/, 'Password may only contain alp
+hanumeric characters' ],
    'key' => [ qr/^[a-fA-F0-9]+$/, 'Key may only contain A-F alphanume
+ric characters' ],
};

$o = OO->new( user => 'username' );
$o->password( 'secret' );
$o->key( '***Invalid' );
$o->no_exist( 'foo' );

print "Password: ", $o->password(), $/;
print "Input errors:\n" . $o->error() if $o->error();
use Data::Dumper;
print Dumper $o;

sub new {
    my $class = shift;
    my $self = { error => '' };
    bless $self, $class;
    $self->init(@_) if @_;
  return $self;
}

sub init {
    my ( $self, %props ) = @_;
    for my $prop ( keys %props ) {
       my $value = $props{$prop};
       $self->$prop( $value );
    }
}

sub AUTOLOAD {
    my ( $self, $value ) = @_;
    my ( $method ) = $AUTOLOAD =~ m/::([^:]+)$/;
    if ( $properties->{$method} ) {
        if ( defined $value ) {
            # its a set method
            if ( $value =~ m/$properties->{$method}->[0]/ ) {
                $self->{$method} = $value;
            }
            else {
                $self->error( $properties->{$method}->[1] . "\n" );
            }
        }
        else {
            # we have a get method
            return $self->{$method};
        }
    }
    else {
        $self->error("Unknown method $method called from " . (join ' '
+, caller()) . "\n" );
    }
}

sub error {
    my ( $self, $error ) = @_;
    $self->{error} .= $error if $error;
  return $self->{error};
}

__DATA__
Password: secret
$VAR1 = bless( {
                 'error' => 'Key may only contain A-F alphanumeric cha
+racters
Unknown method no_exist called from OO C:\\PROGRA~1\\PERLBU~1\\debug\\
+oo 15
',
                 'password' => 'secret',
                 'user' => 'username'
               }, 'OO' );
Input errors:
Key may only contain A-F alphanumeric characters
Unknown method no_exist called from OO C:\PROGRA~1\PERLBU~1\debug\oo 1
+5
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