str = 'abcdefgh'
n = 2
m = 3
puts str[n, m] #=> cde
puts str[n..m] #=> cd
puts str[n..-1] #=> cdefgh
puts str[0..-2] #=> abcdefg
puts str[str.index('d'), m] #=> def
puts str[str.index('de'), m] #=> def
puts str[/a.*d/] #=> abcd
