arrays - Ruby - variable is incremented in one place, but shows as default in another -

i declare $a, , later, in loop, increment , pass widget, however, when @ output widget generating, $a perpetually 1. how can math stored in array work loop-incremented $a?

please excuse newbie code smell- also, dumbed-down version of building, attempt @ solving project euler #128

    $a = 1     $arr = array.new     $step1 = [1, $a-1, -1]     $step2 = [$a+6, -5, 2]      def widget(t,u,v)         t.each |math|             $arr.push (v+math)/u         end     end     (1..100).each |num|         if num % 2 == 0             $a += 1         end     if [something]         widget($step1,$a,num)     elsif [something else]         widget($step2,$a,num)     end 

the use of global variable makes pretty difficult read code, noted $step1 , $step2 evaluated before $a increment, value constant, computed $a == 1:

$step1 = [1, 0, -1] # [1, (1)-1, -1]  $step2 = [7, -5, 2] # [(1)+6, -5, 2]   

if not desired behaviour, should move these 2 statements before if [something] or transform step1 , step2 global variables functions.