#!/usr/bin/perl
use warnings;
use strict;
use Data::Dumper qw/Dumper/;

my %opts = (
    a => [qw/1 2 3/],
    b => [qw/4 5 6/],
    c => [qw/foo bar baz/],
);

# The work function should expect a hashref containing the values
# for this run
my $work = sub {
    my $hr = shift;
    print "A $hr->{a} B $hr->{b} C $hr->{c}\n";
};

run_all_perms(\%opts, $work);
exit 0;

sub run_all_perms {
    my $orig_opts = shift;
    my $work = shift;

    my %multi_opts = %$orig_opts;

    my @keys = sort keys %multi_opts;
    my $key = $keys[0];
    # We don't want to pass this key on
    my $vals = delete $multi_opts{$key};

    foreach my $val (@$vals) {
        if (keys %multi_opts) {
            # We have more perms to do
            my $new_work = sub {
                my $hr = shift;
                # Capture this arg in the hashref
                $hr->{$key} = $val;
                # Run the previous work function with the accumulated args
                $work->($hr);
            };
            # Recurse with our accumulating work function
            run_all_perms(\%multi_opts, $new_work);
        }
        else {
            # We've captured all the args we need, let's go
            $work->({$key => $val});
        }
    }
}