Ruby: why do while and until not return last line they execute from a function? -

I hope the loop of a time comes back to execute the last statement, but does not return a function Does

(1) It starts working ..

  [10] pry (main)> Counter = 0 = & gt; 0 [11] PRI (Main) & gt; A = counter + = 1 while the counter & lt; 10 = & gt; Nil [12] PRI (Main) & gt; A = & gt; 10   
  (2)  This does not work as much as I expected. I hope 10 will be returned and stored in  b .  
  [19] Pry (main)> gt; Def increase (Terminal_value) [19] PRI (Main) * Counter = 0 [19] PRI (Main) * While counter & lt; Terminal_Value [19] PRI (Main) * Counter + = 1 [19] PRI (Main) * End [19] PRE (Main) * end = & gt; : Increase in salary [20] PRI (Main)> B = increment (10) = & gt; Nil [21] PRI (Main) & gt; B = & gt; Zero   
  Question:   
 
 Why, in  (1) , does  Zero  return from the assignment statement?  
 Why was not  b  assigned to  10 ?   
 Update:   
 Outlined as @DaveNewton, in  (1) , I thought I Was doing:  
  one = (counter + = 1 counter while <10)   
 but I was actually doing:  
  (a = counter + = 1) counter & lt; 10    
 
 
 Both in their instances,  while   Zero .   
 
  while  is a result of  zero  as long as  break  is used to provide value Is done for   
 For the same:  
 
 As a  while  loop  zero  until  Break  is used, by the  result loop.