Ruby

def funny_sort(arr)
    parse = lambda {|str| str.scan(/\d+/).fetch(0, "-1").to_i }
    arr.sort {|x, y| parse.call(x) <=> parse.call(y) }
end

puts funny_sort(["abc", "123", "abc321", "213abc", "1.2", "a.3.2", "-987"])

#=> ["abc", "1.2", "a.3.2", "123", "213abc", "abc321", "-987"]
# key = -1,  1,     3,       123,   213,      321,      987