Hello kdjantzen,

As tobyink says, you’re better off not setting a default value — especially as you overwrite it immediately in sub BUILD anyway. However, in the unlikely event that you really do have a use case for this, follow the advice of the error message generated when setting default => \qr//:

References are not allowed as default values, you must wrap the defaul
+t of 're' in a CODE reference (ex: sub { [] } and not []) at ...
[download]

For example, this works:

#! perl
use strict;
use warnings;

package Test
{
    use Moose;

    has re => (is => 'rw', isa => 'RegexpRef', default => sub { qr/abc
+/; });

    sub BUILD
    {
        my $self = shift;

        $self->re(qr/^[0-9]+$/);
    }

    sub match
    {
        my ($self, $string) = @_;

        return $string =~ $self->re ? 'matches' : 'does not match';
    }
}

my $t = Test->new();

print "$_ ", $t->match($_), "\n" for 'abc123def', '456';
[download]

Hope that helps,