$ perl -wle'$|=1; @a=qw(a b c); print "$_: $a[$_]" for -@a-1..$#a+1'
Use of uninitialized value in concatenation (.) or string
-4:
-3: a
-2: b
-1: c
0: a
1: b
2: c
Use of uninitialized value in concatenation (.) or string
3: