split-related functionalities

I use ruby 1.9.2.

gsub/scan iterate over matches to a given regex/string, and is used in three ways:

1. If scan is used without a block, it returns an array of matches.
2. If scan is used with a block, it iterates over matches and performs something.
3. If gsub is used, it replaces the matches with what is given as the second argument or as the block, and returns a string.

On the other hand, there is split that matches the complement of what gsub/scan match. However, there is only one way to use this:

1. If split is used without a block, It returns an array of the complement of the matches.

I wanted the other two missing usages related to split, and tried to implement them. The following every_other extends split so that it can be used like scan.

class String
  def every_other arg, &pr
    pr ? split(arg).to_enum.each{|e| pr.call(e)} : split(arg)
  end
end

# usage:
'cat, two dogs, horse,开发者_开发技巧 three cows'.every_other(/,\s*/) #=> array
'cat, two dogs, horse, three cows'.every_other(/,\s*/){|s| p s} # => executes the block

Then, I tried to implement the counterpart of gsub, but cannot do it well.

class String
  def gsub_other arg, rep = nil, &pr
    gsub(/.*?(?=#{arg}|\z)/, *rep, &pr)
  end
end

# usage
'cat, two dogs, horse, three cows'.gsub_other(/,\s*/, '[\1]') # or
'cat, two dogs, horse, three cows'.gsub_other(/,\s*/) {|s| "[#{s}]"}

# Expected => "[cat], [two dogs], [horse], [three cows]"
# Actual output => "[cat][],[ two dogs][],[ horse][],[ three cows][]"

• What am I doing wrong?
• Is this approach correct? Is there a better way to do it, or are there already methods that do this?
• Do you have suggestions about the method names?

It's not beautiful but this seems to works

s='cat, two dogs, horse, three cows'
deli=",\s"
s.gsub(/(.*?)(#{deli})/, '[\1]\2').gsub(/(.*\]#{deli})(.*)/, '\1[\2]')

=> "[cat], [two dogs], [horse], [three cows]"

The following feels a little better

s.split(/(#{deli})/).map{|s| s!=deli ? "[#{s}]" : deli}.join