>> def foo(bar)
>> bar.call
>> end
=> :foo
>> lambda_with_break = -> { break }
=> #<Proc:0x000055b4c7e21540@(irb):4 (lambda)>
>> proc_with_break = proc { break }
=> #<Proc:0x000055b4c7e28958@(irb):5>
>> foo(lambda_with_break)
=> nil
>> foo(proc_with_break)
Traceback (most recent call last):
        6: from /home/edem/.rvm/rubies/ruby-2.6.6/bin/irb:23:in `<main>'
        5: from /home/edem/.rvm/rubies/ruby-2.6.6/bin/irb:23:in `load'
        4: from /home/edem/.rvm/rubies/ruby-2.6.6/lib/ruby/gems/2.6.0/gems/irb-1.0.0/exe/irb:11:in `<top (required)>'
        3: from (irb):7
        2: from (irb):2:in `foo'
        1: from (irb):5:in `block in irb_binding'
LocalJumpError (break from proc-closure)

In non-lambda procs, break means exit from the method which the block given for. (and will throw LocalJumpError if invoked after the method returns);

def foo
  Proc.new { break }.call
end

LocalJumpError: break from proc-closure
from (pry):19:in `block in foo'