name-value-strstr

This operation matches requests where the specified header (argument1) contains the given substring (argument2) somewhere in its value. The match is case sensitive.

<match:request-header operation="name-value-strstr" argument1="Referer" argument2=".domain.com">

!name-value-strstr: matches if either the given header name is not present or the substring specified in metadata is not part of the header's value.