When to use a new variable vs string interpolation? - ruby

Question

I wrote a script that I decided to refactor so I could add functionality to it as my coworkers think of it. I only saved four lines in the effort, but the main change is I removed both methods and reduced the number of called variables in favor of string interpolation/manipulation. Is there a preference for this? Is it better to declare a new variable just to use once, or is it more DRY to just make minor tweaks to the string when you need to use it? For example here is the original code:
def validate_directory(dir)
puts "Enter the full directory path of the flv files." unless dir
input = dir || gets.chomp
input.gsub!('\\', '/')
input += '/' unless input[-1..-1] == '/'
until File.directory?(input) && Dir.glob("#{input}*.flv") != []
puts "That directory either doesn't exist or contains no .flv files. \nEnter the full directory path of the flv files."
input = $stdin.gets.chomp
input.gsub!('\\', '/')
input += '/' unless input[-1..-1] == '/'
end
dir = input
end
def output(flv, location)
title = flv.dup.gsub!(".flv", ".html")
vid = flv.dup
vid.slice!(0..6)
body = $EMBED.gsub("sample.flv", vid)
htmlOutput = File.open(title, "w")
htmlOutput.write(body)
htmlOutput.close
linkList = File.open("#{location}List of Links.txt", "a")
linkList.write($BASE + vid.gsub(".flv", ".html") + "\n")
linkList.close
puts "Files created successfully."
end
dir = ARGV[0].dup unless ARGV.empty?
folder = validate_directory(dir)
files = folder.clone + "*.flv"
flvs = Dir.glob("#{files}")
File.delete("#{folder}List of Links.txt") if File.exists?("#{folder}List of Links.txt")
flvs.each { |flv| output(flv, folder) }
And the new stuff:
flash_folder = ARGV[0].dup unless ARGV.empty?
if !flash_folder
puts "Enter the full directory path of the flv files."
flash_folder = gets.chomp
end
flash_folder.gsub!('\\', '/')
flash_folder += '/' unless flash_folder[-1..-1] == '/'
until File.directory?(flash_folder) && Dir.glob("#{flash_folder}*.flv") != []
puts "That directory either doesn't exist or contains no .flv files. \nEnter the full directory path of the flv files."
flash_folder = $stdin.gets.chomp
flash_folder.gsub!('\\', '/')
flash_folder += '/' unless flash_folder[-1..-1] == '/'
end
flash_files = Dir.glob("#{flash_folder}*.flv")
File.delete("#{flash_folder}List of Links.txt") if File.exists?("#{flash_folder}List of Links.txt")
flash_files.each do |flv|
html_output = File.open("#{flv.gsub(".flv", ".html")}", "w")
html_output.write("#{embed_code.gsub("sample.flv", flv.slice(7..flv.length))}")
html_output.close
link_list = File.open("#{flash_folder}List of Links.txt", "a")
link_list.write("#{flash_url}#{flv.slice(2..flv.length).gsub(".flv", ".html")}\n")
link_list.close
end
puts "Finished."