Functional Programming in Perl

Syntactic Difficulties

Here's a most substantial example
In ML for the Working Programmer, Paulson presents a parsing system
A parser is a function of type:

           char list -> 'a * char list

For example:

        fun digit (in1::ins) =
          if in1 = '0' then (0, ins) else
          if in1 = '1' then (1, ins) else
          ...
          if in1 = '9' then (9, ins) else
          raise "Parse error..."

Now you want some parser combinators:

        fun nothing input = ((), input);

        fun concat p1 p2 input =
          let val (v1, i1) = p1 input in
          let val (v2, i2) = p2 i1    in
            ((v1, v2), i2)
          end end

        fun star p1 input =
          alternates(concat(p1, star p1), nothing);