I think you're looking for index. From perldoc -f index:

       index STR,SUBSTR,POSITION
       index STR,SUBSTR
               The index function searches for one string within another, but
               without the wildcard-like behavior of a full regular-expression
               pattern match.  It returns the position of the first occurrence
               of SUBSTR in STR at or after POSITION.  If POSITION is omitted,
               starts searching from the beginning of the string.  The return
               value is based at 0 (or whatever you'e set the $[ variable
               to--but don't do that).  If the substring is not found, returns
               one less than the base, ordinarily "-1".