Combinations are distinct subsets of a set. So I am not sure what the Python snippet is really meant to produce. If I were asked to produce all combinations of words in a string, I'd use the theory that the number of subsets of a set of N members is 2**N. The reason is that a bit-string of N bits, where each bit represents inclusion of an element, represents a combination and all possible combinations can therefore be represented by all possible numbers expressed as these bit strings from 0 to (2**N)-1 (of which there are 2**N, including the empty set). So converting the theory into Perl:-

Update: I just noticed the OP wants to vary separators not words, so I'll address that further down...

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";
}
[download]

which produces the following output:

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
[download]

Update: to vary spaces and hyphens (what I now understand is wanted), the same technique can apply

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 '-';
        }
    }
}
[download]

producing

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
[download]

More update: Afterthought: 1 << $var is likely to be faster than, while being equivalent to:  2 ** $var.

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