"Escape" escaped.
The original specifications of prometheus contain sample patterns with regex:

{__name__=~"<regex>"} {__name__=~"process_cpu_sec.+"}

But all versions of our current documentation has a backslash in front of ~:

{__name__=\~"<regex>"} cpu_usage_system{cpu=\~".*"}

This format is not accepted by Zabbix and gives an error:
Pattern: Invalid Prometheus pattern.
removal of the backslash fixed this.