Functional Programming in Perl

Simple closure example

        (* SML *)
        fun mkcounter a' =
          let val a  = ref a'
              fun f = (a := !a + 1; print (toStr (!a)))
          in f 
          end

        # Perl
        sub mkcounter {
          my $a = shift;
          my $f = sub { $a++; print "$a\n" };
          return $f;
        }