my @probs =(0,0.1,0.53,0.51,0.59,0.67,0.2,0.04,0.05,0.56,0.89,0.75);

##</code><code>##

2 5
9 11

##</code><code>##


my $positions = undef;
my @segment=();
foreach (0..$#probs){
 if ($probs[$_]>0.5 && $probs[$_+1]>0.5){
  $positions = $positions.','.$_;
 }
 else {push @segment, $positions if ($positions); $positions = undef}
}