this Expression use conditional expression to eveluate parameter after "HREF" and executes the yes/no part of the expression. this expression finds <A> TAG and returns value of "HREF" and the value hold in between <a></a> tags. the expression returns maximum 3 sub matches. the first match returns the "HREF" tag value and rest of two holds the value of the tag alternativly. so after executing the expression you need to itarate through all the submatches and need to find out non NULL tags to get value.
the output of the above matching expamples would be like this :
3: or NULL
the output of the second matching example would be like this.
2: or NULL