What is the pipe operator "|>" in BigQuery SQL?

The following SQL is not valid:

WITH foo AS (SELECT 1)
FROM bar a
WHERE x = y

However, it produces an interesting error message in the BigQuery UI:

Syntax error: WHERE not supported after FROM query; Consider using pipe operator `|> WHERE` at [3:1]

I like pipe operators in general, so I Googled but found nothing.

ChatGPT told me something, so I tested it

SELECT * FROM bigquery-public-data.samples.shakespeare
|> WHERE word_count > 100

but I can not make it work.

Pipe query syntax not supported at [2:1]

(Maybe it simply hallucinated.)

So what is the pipe operator "|>" in BigQuery SQL and how can it be used?

To date, an enrollment form must be completed to use the pipe operator: https://cloud.google.com/bigquery/docs/pipe-syntax-guide