Ruby Shuffle word letters

Shuffle letters of a sequence of wodrs except for the first and last letters.

#!/usr/bin/env ruby
#
# Shuffle letters of a sequence of wodrs except for the first
# and last letters.
#

def isalpha(word)
	if ("a" .. "z") === word[0] || ("A" .. "Z") === word[0]
		return true
	end

	return false
end

def scramble(word)
	if (word.length <= 3)
		return word
	end

	return word[0] +
		word[1 .. word.length - 2].split(//).shuffle().join() +
		word[word.length - 1]
end

loop {
	line = gets()
	if line == nil
		break
	end

	tokens = line.chomp().split(/( |\[|\]|\(|\)|\"|\.|\?|\!|\/|\\|\:|\,)/)

	tokens.each do |token|
		if isalpha(token)
			token = scramble(token)
		end

		printf("%s", token)
	end
	puts
}