#!/usr/bin/perl

use strict;
use warnings;

my $state = 0;   # 0 - light off, 1 - light on

my $uplim = 102; # upper limit
my $lolim =  98; # lower limit
my $n = 3;       # 
my $counter = 0;

# Set initial state
# This part may need more work in order to avoid eventual starting glitch.
my $value = <DATA>;
chomp $value;

if ($value > (($uplim + $lolim) / 2.0)) {
  $state = 1;
} else {
  $state = 0;
}

# work continuously
while ($value = <DATA>) {
  chomp $value;

  # Adjust counter
  if ($value > $uplim) {
    if ($counter < 0) {
      $counter = 0;
    } else {
      $counter++;
    }
  } elsif ($value < $lolim) {
    if ($counter > 0) {
      $counter = 0;
    } else {
      $counter--;
    }
  } else {
    $counter = 0;
  }

  # Set state
  if ($counter > $n) {
    $state = 1;
  } elsif ($counter < -$n) {
    $state = 0;
  }

  # Print
  my ($below, $between, $above);
  $below = $between = $above = '---';

  if ($value > $uplim) {
    $above = $value;
  } elsif ($value < $lolim) {
    $below = $value;
  } else {
    $between = $value;
  }

  printf "state: %d cnt: %+3d %3s<%3d>%3s<%3d>%3s\n", $state, $counter, $below, $lolim, $between, $uplim, $above;
}

__DATA__
100
101
102
103
104
105
106
105
104
103
102
101
100
99
98
97
96
95
94
101
102
103
103
102
103
103
104
104