gistfile1.txt

package Class;
use Moose;
use Moose::Util::TypeConstraints;

## Whatever, you get the idea.
sub trim_whitespace { my $str = shift; $str =~ s/^\s+|\s+$//; $str };
sub boolify {  my $str = shift; $str =~ /^y/i ? 1 : $str };

## Guess i need to say an OLBool is just a regular bool that coerces, stringifies, and removes padding... JOYZER. Shouldn't the where be at the very least, inherited it is a subtype.

subtype 'OLBool' => as 'Bool' => where { /1|0/ };
coerce 'OLBool'
  => from 'Str' => via { boolify( trim_whitespace($_) ) }
;
has 'foo' => ( isa => 'OLBool', is => 'rw',
  coerce => 1, # HTH
);

my $c = Class->new;

printf ( "Should get %s\n", boolify(trim_whitespace('y')) );
$c->foo( 'y' ); ## EXCPETION

die $c->foo;