Add an extra datum to @probs and the output layout goes a bit ga ga as well.

$ cat spw759180_NetWallah 
#!/usr/bin/perl
#
use strict;
use warnings;

my @probs =(0,0.1,0.53,0.51,0.59,0.67,0.2,0.04,0.05,0.56,0.89,0.75,0.6
+);
my $t;
print $_ . (",","\n")[$t=1-$t]  
    for  grep {($probs[$_] >=.5 .. $probs[$_]> .5) and $t=!$t }
           0..$#probs
$ ./spw759180_NetWallah
2
4,9
11,$

[download]

I think you have to separate the task of finding the in-range values from that of determining the range boundaries as you have no idea what the next datum will be when processing the current one. Also, I think the start and stop conditions of the flip-flop should be consistent (and both > 0.5 since that is the requirement in the OP). In the following code I've added some data to show how single-element ranges are treated.

use strict;
use warnings;

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,
   0.1,
   0.51,
   0.6,
   0.2,
   0.7,
   );

my @inRange =
   grep { $probs[ $_ ] > 0.5 .. $probs[ $_ ] > 0.5 }
   0 .. $#probs;

my @starts =
   map  { $inRange[ $_ ] }
   grep {
            $_ == 0
            ||
            $inRange[ $_ ] - $inRange[ $_ - 1 ] != 1
        }
   0 .. $#inRange;

my @ends =
   map  { $inRange[ $_ ] }
   grep {
            $_ == $#inRange
            ||
            $inRange[ $_ + 1 ] - $inRange[ $_ ] != 1
        }
   0 .. $#inRange;

printf qq{%3d%3d\n}, $starts[ $_ ], $ends[ $_ ] for 0 .. $#starts;

[download]

The output.

  2  5
  9 11
 13 14
 16 16

[download]

I hope this is of interest.

Cheers,

JohnGG

In reply to Re^2: printing array positions that match a condition by johngg
in thread printing array positions that match a condition by coldy

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