$global_var_altered = false
$threads{}
freq = [1,2,3...]

object = Object.new

freq.each do |num|
    $threads[num] = Thread.new {object.function_that_changes_global_var}
end

$threads.each do |thr|
  thr.join
  $threads.delete(thr[0])
end

p $global_var_altered