Heres a code snippet which could help you a bit ...
didnt use it for a long time, but AFAIR it works and returns all possible permutations for the given string.

sub DoPermuteArray {

  my @array = @{ $_[0] };
  my @permuted;

  eval (&PermuteArray(['1','1','1','1','-','--'],[],\@permuted));

  return @permuted;
}

sub PermuteArray {
# taken from the perl FAQ

  my @items = @{ $_[0] };
  my @perms = @{ $_[1] };
  my $permuted = $_[2];
  my @return;

  unless (@items) {
    push (@$permuted,[@perms]);
  } else {

    my(@newitems,@newperms,$i);

    foreach $i (0 .. $#items) {

      @newitems = @items;
      @newperms = @perms;
      unshift(@newperms, splice(@newitems, $i, 1));
      &PermuteArray ([@newitems], [@newperms]);

    }
  }

}
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Rgds.
Gnork