https://bugs.ruby-lang.org/issues/6284#change-73367

compose_procs.rb

class Proc
  def >> other
    -> arg { other.to_proc.call call arg }
  end

  def << other
    -> arg { call other.to_proc.call arg }
  end
end

add_forty_two = -> x { x + 42 }

[1, 3, 6].map &:abs2.to_proc << add_forty_two
#=> [1849, 2025, 2304]

[1, 3, 6].map &:abs2.to_proc >> add_forty_two
#=> [43, 51, 78]

[:hi, :there].map &:to_s.to_proc << :upcase
#=> ["HI", "THERE"]

[:hi, :there].map &:to_s.to_proc >> :upcase >> :reverse
#=> ["IH", "EREHT"]

[:hi, :there].map &:reverse.to_proc << :upcase << :to_s
#=> ["IH", "EREHT"]

Looks like Proc#>> and Proc#<< are swapped - results are not the same as in comments.

Symbol methods are not required, because only first symbol need to be converted explicitly:

[:hi, :there].map &:to_s.to_proc << :upcase << :reverse

This is be better because symbols should not be tied with functional computations. At least in stdlib.

Ah, interesting. Thank you for the feedback! I'll update the gist.