Using a mixin to extend the object instance with the functionality we want

files2.rb

module Logfiles
  def name
    self.sub(/\.gz$/)
  end

  def skip?
    !(@options[:unzip] && self.gzip?)
  end

  def gzip?
    self.match(/\.gz$/)
  end

  def cleanup
    system "gzip #{self.name}" if self.gzip?
  end
end

Dir['*'].each do |file|
  file.extend Logfiles

  next if file.skip?

  IO.foreach(file.name) do |line|
    #...
  end

  file.cleanup
end

Nice example for extending objects. I riffed off your idea and tried to improve it with some custom enumeration.

# Usage:
#
#     LogDir['*'].each do |file|
#        ...
#     end
class LogDir
  module Gzip
    def gunzip
      system "gunzip #{self}" if gzipped?
    end

    def gzip
      system "gzip #{self.gunzipped}" if gzipped?
    end

    def gzipped?
      File.extname(self) == ".gz"
    end

    def gunzipped
      File.basename(self, ".gz")
    end
  end

  def self.[](path)
    new( Dir[path] )
  end

  def initialize(entries)
    @entries = entries.map { |e| e.extend(Gzip) }
  end

  def each
    @entries.each do |entry|
      entry.gunzip
      yield entry.gunzipped
      entry.gzip
    end
  end
end

I like the riff generalization