my $string = "....";
my $regex = qr/...(...).../; # must have $1 be the thing we're optimizing to reduce
my @solutions;
while ($string =~ g/(?=$regex)/g) {
  push @solutions, [[@-], [@+]]; # push starts and ends
}
# now walk through the solutions, and pick the one with the minimal span on $1
# [ code unfinished ]