The delimiter for arguments in Google Sheets formulas varies based on country and locale. It can either be a comma or semi-colon. The only way to detect the proper delimiter is by retrieving the spreadsheet's locale using `SpreadsheetApp.getActiveSpreadsheet().getSpreadsheetLocale();`, then mapping that value using the data below. I manually got…

locales.json

{
  "en_US": ",",
  "es_AR": ";",
  "hy_AM": ";",
  "en_AU": ",",
  "az_AZ": ";",
  "be_BY": ";",
  "es_BO": ";",
  "pt_BR": ";",
  "bg_BG": ";",
  "en_CA": ",",
  "fr_CA": ";",
  "es_CL": ";",
  "zh_CN": ",",
  "es_CO": ";",
  "hr_HR": ";",
  "cs_CZ": ";",
  "da_DK": ";",
  "es_EC": ";",
  "ar_EG": ",",
  "fi_FI": ";",
  "fr_FR": ";",
  "ka_GE": ";",
  "de_DE": ";",
  "el_GR": ";",
  "zh_HK": ",",
  "hu_HU": ";",
  "hi_IN": ",",
  "bn_IN": ",",
  "gu_IN": ",",
  "kn_IN": ",",
  "ml_IN": ",",
  "mr_IN": ",",
  "pa_IN": ",",
  "ta_IN": ",",
  "vi_VN": ",",
  "in_ID": ";",
  "en_IE": ",",
  "it_IT": ";",
  "ja_JP": ",",
  "kk_KZ": ";",
  "lv_LV": ";",
  "lt_LT": ";",
  "es_MX": ",",
  "mn_MN": ",",
  "my_MM": ",",
  "nl_NL": ";",
  "no_NO": ";",
  "nn_NO": ";",
  "es_PY": ";",
  "fil_PH": ",",
  "pl_PL": ";",
  "pt_PT": ";",
  "ro_RO": ";",
  "ru_RU": ";",
  "sr_RS": ";",
  "sk_SK": ";",
  "sl_SI": ";",
  "ko_KR": ",",
  "es_ES": ";",
  "ca_ES": ";",
  "sv_SE": ";",
  "de_CH": ",",
  "zh_TW": ",",
  "th_TH": ",",
  "tr_TR": ";",
  "uk_UA": ";",
  "en_GB": ",",
  "cy_GB": ",",
  "es_UY": ";",
  "es_VE": ";"
}