require 'erb'

html_erb = ""
('A' .. 'G').to_a.each do |col|
  puts col

  html_erb << 'yo <%= blabla(col) %>'
end

puts ERB.new(html_erb).result

(erb):1: undefined local variable or method `col' for main:Object (NameError)
A
B
C
D
E
F
G