package Artificial::Example;
use Carp;

sub integer_rx {
  # params ($self, $item) ignore $self
  for my $item ($_[1]) { # alias
    unless ($item =~ s/^\s*([-+])?\s*(\d+)\s*$/$1$2/) {
      confess "You must provide a valid number, (not '$item')";
    }
  }
  return 1;
}

sub validate_item {
  my $self = shift;
  for my $item ($_[0]) { # alias

    my $constraint = 'integer_rx';
    $self->$constraint($item);
    return 1;
  }
}

my $slot = bless {} => __PACKAGE__;

my @tests = ('123','  + 456 ', 'zzz');
for my $item (@tests) {
    print "'$item' before check\n";
    $slot->validate_item($item);
    print "'$item' after check\n\n";
}

1;
__END__

$ perl -w for_alias.pl 
'123' before check
'123' after check

'  + 456 ' before check
'+456' after check

'zzz' before check
You must provide a valid number, (not 'zzz') at for_alias.pl line 7
        Artificial::Example::integer_rx('Artificial::Example=HASH(0x80
+f606c)', 'zzz') called at for_alias.pl line 19
        Artificial::Example::validate_item('Artificial::Example=HASH(0
+x80f606c)', 'zzz') called at for_alias.pl line 29
[download]