Have you tried prototypes?

Briefly. I don't fully grok the try/catch example in perldoc perlsub, so I may be missing something, but my failed attempts look like:

#! /usr/bin/perl

use strict;
use warnings;

sub curry(&@)
{
    my ($fn, @args) = @_;

    return sub {
        $fn->(@args, @_);
    }
}

&curry(+, 2)->();
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I'm thinking that a source filter might help, turning builtins used as values into anonymous subs, but I don't know very much about source filters — I'm not even sure that they do what I think they do.

Perhaps I misunderstood what you wanted. While you are certainly in trouble if you want to curry the + operator, I see no problem with a function such as sum.

use strict;
use warnings;
use List::Util qw(sum);

sub curry(&@)
{
    my ($fn, @args) = @_;
    return sub {
        $fn->(@args, @_);
    }
}

my $f = curry { sum(@_) } 5;

print $f->(3); # prints 8 (5 + 3)
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Check out the functions in Object::Iterate, where I define the imap and igrep functions. I discuss this in my Iterator Design Pattern article for The Perl Review 0.5 (September 2002).

The next issue of The Perl Review will include "Functional Programming in Perl" which discusses higher order functions in Perl.

--
brian d foy <bdfoy@cpan.org>

I was refering to the idea that prototypes allow you to imitate the way builtins such as grep and map are called (without having to say "sub", but now I'm not so sure if it that was the issue).

It wasn't. I just noticed that my original node was a bit vague about why I didn't like the builtin/user function distinction; I've updated it. Sorry about the confusion.

--
Yours in pedantry,
F o x t r o t U n i f o r m
"Anything you put in comments is not tested and easily goes out of date." -- tye