GA4 view_item tracking

I’m trying to track more information in GA4.
I have added this to my product template, to log events when someone views an item:

gtag("event", "view_item", {
  currency: "GBP",
  value:  [[+product_info.price]],
  items: [
      item_id: "[[+product_info.sku]]",
      item_name: "[[*longtitle:default=`[[*pagetitle]]`]]",
      index: 0,
      price: [[+product_info.price]]

But the price comes out in ‘cents’. e.g. a product which is £4.00 is displayed in the above tag as ‘400’. I thought I could use output modifiers to divide the value by 100, but if I try:

price: [[+product_info.price:div=`100`]]

I get no value at all.

Any idea?