1. If you have a block of the form { |v| v.mtd }:

ary.each { |v| v.mtd } # normal way
ary.each(&:mtd) # simpler way

# Example:
ary = %w(abc def ghi jkl)
ary.each(&:upcase!) # same as ary.each { |v| v.upcase! }

That works for other Array methods, like map. More on it.

2. If you have a block of the form { |v| mtd v }, and the method mtd does the same thing with all parameters:

ary.each { |v| mtd v } # normal way
mtd *ary # simpler way

#Example:
ary = %w(abc def ghi jkl)
puts *ary # same as ary.each { |v| puts v }

See more on it.