my @superset = split /\s+/, 'convert python to perl';
my $N = scalar @superset;
for my $combo (0..((2**$N) - 1)) {   # a combo is also a bit mask
    print "selection:";
    for my $selector (0..($N-1)) {  # a selector is also a bit
	(2**$selector) & $combo and print ' ' . $superset[$selector];
    }
    print "\n";
}

##</code><code>##

selection:
selection: convert
selection: python
selection: convert python
selection: to
selection: convert to
selection: python to
selection: convert python to
selection: perl
selection: convert perl
selection: python perl
selection: convert python perl
selection: to perl
selection: convert to perl
selection: python to perl
selection: convert python to perl

##</code><code>##

my @superset = split /\s+/, 'convert python to perl';
my $N = $#superset; # one less element than in the previous example
for my $combo (0..((2**$N) - 1)) { # a combo is a bit mask
    for my $selector (0..$N) {  # a selector is also a bit position
        print $superset[$selector];
        if ($selector == $N) {
            print "\n";
	    next;
        }
	if ((2**$selector) & $combo) {
            print ' ';
        }
        else {
            print '-';
        }
    }
}


##</code><code>##

convert-python-to-perl
convert python-to-perl
convert-python to-perl
convert python to-perl
convert-python-to perl
convert python-to perl
convert-python to perl
convert python to perl