#!/usr/bin/perl 
use strict;
use Data::Dump qw(dd pp);
use List::Util qw(reduce shuffle);

# the composables
sub Cmp  { my ($x, $y) = @_; $x cmp $y }
sub Ncmp { my ($x, $y) = @_; $x <=> $y }
sub Reverse   { map { scalar reverse $_ } @_ }
sub Length    { map { length $_ } @_ }
sub Uc        { map { uc $_ } @_ }
sub Transpose { reverse @_ }
sub Ab        { ($a, $b) }

# naive composer using evil
# composes functions f, g, h into sub { f(g(h(@_))) }
sub Compose {
    my $body = reduce { "$b($a)" } '@_', reverse @_;
    eval "sub { $body }" or die $@;
}

# special case for sort
sub Compose_ab { Compose(@_, 'Ab') }

sub sorter {
    my ($type, $src) = @_;

    # Legend:
    # i = case insensitive
    # a = ascending
    # d = descending
    # r = reverse (right to left)
    # n = numbers
    # l = length of value

    my %sorter = (
        a   => [qw/Cmp/],
        d   => [qw/Cmp Transpose/],
        ai  => [qw/Cmp Uc/], 
        di  => [qw/Cmp Uc Transpose/],
        an  => [qw/Ncmp/],
        dn  => [qw/Ncmp Transpose/],
        al  => [qw/Ncmp Length/],
        dl  => [qw/Ncmp Length Transpose/],
        ar  => [qw/Cmp Reverse/],
        dr  => [qw/Cmp Reverse Transpose/],
        air => [qw/Cmp Uc Reverse/],
        dir => [qw/Cmp Uc Reverse Transpose/],
    );

    my @composed;
    if ($type) {
        $type = join '', sort split //, $type; # normalize
        @composed = @{ $sorter{$type} }
          or die "Unknown option: $type";
        if ($src) {
            push @composed, $src;
        }          
    }
    else {
        @composed = @{ (shuffle values %sorter)[0] };
        warn 'random criteria: ' . pp @composed;
    }
    return Compose_ab(@composed);
}

my @unsorted = qw(red lilac yelloW Green cyan blue magenta);
my $sort_type = shift;
my $criteria = sorter($sort_type);
dd sort $criteria @unsorted;

my %master_list = (
    alpha => { members => 1 },
    beta  => { members => 3 },
    gamma => { members => 8 },
    delta => { members => 5 },
);

# custom source for $a, $b
sub Members { map { $master_list{$_}{members} } @_ }
$criteria = sorter($sort_type, 'Members');
dd sort $criteria keys %master_list;