Use reverse indexing:
[1..-1]
An element in Ruby (and some other languages) has straight forward index and a “reversed” one. So, string with length n has 0..(n-1) and additional (-n)..-1 indexes, but no more — you can’t use >=n or <-n indexes.
'i' 'n'|'A' 'u' 's' 't' 'i' 'n'|'A' 'u' 's' 't' 'i' 'n'|'A' 'u' 's'
-8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8
<- error | you can use this | error ->