regexp_interfaces_list:
      - "^mgmt[0-9]{1}|^[fFgGhHtT]{1}[a-zA-Z]{3,9}Ethernet[0-9]{1,2}([/][0-9]){1,3}[\\.0-9]{0,4}|"
      - "^port-channel[0-9]{1,4}[\\.0-9]{0,4}|"
      - "^Vlan[0-9]{1,4}|"
      - "^loopback[0-9]{1,4}"

- debug:
    var: regexp_interfaces_list

- debug:
    var: "{{regexp_interfaces_list | join }}"

RESULTS:

TASK [NXOS_Facts : debug] *******************************************************************************************************************************************************************************************************************
ok: [3064-01] => {
    "regexp_interfaces_list": [
        "^mgmt[0-9]{1}|^[fFgGhHtT]{1}[a-zA-Z]{3,9}Ethernet[0-9]{1,2}([/][0-9]){1,3}[\\.0-9]{0,4}|",
        "^port-channel[0-9]{1,4}[\\.0-9]{0,4}|",
        "^Vlan[0-9]{1,4}|",
        "^loopback[0-9]{1,4}"
    ]
}

TASK [NXOS_Facts : debug] *******************************************************************************************************************************************************************************************************************
An exception occurred during task execution. To see the full traceback, use -vvv. The error was:   line 1
fatal: [3064-01]: FAILED! => {"msg": "Unexpected failure during module execution.", "stdout": ""}