This example demonstrages the match function which has the following form: 
match(string, regexp) 

The match function searches the string, string, for the longest, leftmost substring matched by
the regular expression, regexp. It returns the character position, or index, of where that
substring begins (1, if it starts at the beginning of string). If no match if found, it returns 0.
The match function sets the built-in variable RSTART to the index. It also sets the built-in
variable RLENGTH to the length in characters of the matched substring. If no match is found,
RSTART is set to 0, and RLENGTH to -1. For example: 

     awk '{
            if ($1 == "FIND")
              regex = $2
            else {
              where = match($0, regex)
              if (where)
                print "Match of", regex, "found at", where, "in", $0
            }
     }'