occurred during the expect rule evaluation. <fmt> is a
Custom log format string (see section 8.2.6).
+ status-code <expr> is optional and can be used to set the check status code
+ reported in logs, on success or on error. <expr> is a
+ standard HAProxy expression formed by a sample-fetch
+ followed by some converters.
+
<match> is a keyword indicating how to look for a specific pattern in the
response. The keyword may be one of "status", "rstatus", "hdr",
"fhdr", "string", or "rstring". The keyword may be preceded by an