I' using the function "expression_is_true" with a regex in "expression" and I have some problem with the "//d" can someone give me some advice?

- expression_is_true:
             tags: ['CONF_DTYP']
             expression: "customer_type = 'Persona Fisica' AND NOT REGEXP_CONTAINS(FORMAT_DATE('%Y/%m/%d', birth_date), '^\\d{4}/\\d{2}/\\d{2}$')"