Ruby 2.7 introduced numbered parameters for blocks

Since Ruby 2.7, it is possible to use numbered parameters in blocks additionally to named parameters.

This is an example of a block with named parameters:

my_array.each { |element| element.do_something }

And this is the same line with numbered parameters:

my_array.each { _1.do_something }

This works with multiple parameters too:

# named parameters
my_hash.each_pair { |key, value| puts "#{key}: #{value}" }

# numered parameters
my_hash.each_pair { puts "#{_1}: #{_2}" }