Create new data type for a compiled regular expression; this type

Create new data type for a compiled regular expression; this type
contains the case-fold information used to compile the regexp.  Modify
the low-level regular-expression procedures to accept this new type
and to no longer have an argument for case-fold.  Modify the
high-level regular-expression procedures to accept a compiled regular
expression in place of a regular-expression string; in this case the
optional case-fold argument is ignored.

Edit all references to the low-level procedures to conform to this new
design.