An example with procs, blocks and lambdas in Ruby

.rb

lambda_1 = -> { puts 'From lambda_1: Hello, World!' }
lambda_2 = -> { puts 'From lambda_2: Hello, World!' }

proc_1 = Proc.new { puts 'From proc_1: Hello, World!' }
proc_2 = Proc.new { puts 'From proc_2: Hello, World!' }

def proc_or_lambda_called(
	proc_or_lamdba_1,
 	proc_or_lamdba_2
)
	proc_or_lamdba_1.call
	proc_or_lamdba_2.call

	yield if block_given?
end

# without block
proc_or_lambda_caller(lambda_1, lambda_2)
proc_or_lambda_caller(proc_1, proc_2)

# with block
proc_or_lambda_caller(lambda_1, lambda_2) do
	puts "From the default allowable block: Hello, World!"
end
proc_or_lambda_caller(proc_1, proc_2) do
	puts "From the default allowable block: Hello, World!"
end

# Output:
#
# From lambda_1: Hello, World!
# From lambda_2: Hello, World!
# From proc_1: Hello, World!
# From proc_2: Hello, World!
# From lambda_1: Hello, World!
# From lambda_2: Hello, World!
# From the default allowable block: Hello, World!
# From proc_1: Hello, World!
# From proc_2: Hello, World!
# From the default allowable block: Hello, World!