state $validate = compile(slurpy Dict[ prefix => DBPrefix ]); #per the docs for named args
my ($param) = $validate->( @_ );

# in foo.pl
$obj->method( 'bar' );

# output :
# Reference {"prefix" => "bar"} did not pass type constraint "Dict[prefix=>DBPrefix]" (in $SLURPY) at ./foo.pl line 11