The Match Characters, Return Relative Position routine searches a
    source string for a specified substring and returns an index,
    which is the relative position of the first occurrence of a
    substring in the source string. The relative character positions
    returned by LIB$MATCHC are numbered 1, 2, . . . , n. Thus, zero
    means that the substring was not found.

    Format

      LIB$MATCHC  sub-string ,source-string