Ruby each_with_index offset
some_array.each_with_index{|item, index = 1| some_func(item, index) }

[:foo, :bar, :baz].to_enum.with_index(1).each do |elem, i|
  puts "#{i}: #{elem}"
end

1: foo
2: bar
3: baz

some_array.each_with_index{|item, index| some_func(item, index+1)}

some_array.each_with_index{|item, i| j = i + 1; some_func(item, j)}

module Enumerable
  def each_with_index_from_one *args, &pr
    each_with_index(*args){|obj, i| pr.call(obj, i+1)}
  end
end

%w(one two three).each_with_index_from_one{|w, i| puts "#{i}. #{w}"}
# =>
1. one
2. two
3. three

offset = 2
some_array[offset..-1].each_with_index{|item, index| some_func(item, index+offset) }

some_array[offset..-1].each_with_index{|item, index| some_func(item, index) }
some_array[offset..-1].each_with_index{|item, index| some_func(item, index+offset) }
some_array[offset..-1].each_with_index{|item, index| index+=offset; some_func(item, index) }

some_array[1000,-1] => nil
nil.each_with_index => Error 'undefined method `each_with_index' for nil:NilClass'

(some_array[offset..-1]||[]).each_with_index{|item, index| some_func(item, index) }

offset = 1000
 some_array[offset..-1].each_with_index{|item, index| some_func(item, index) } if offset <= some_array.size