$ perl -le"$_ = 123456; s/./warn pos; warn q,  ,, pos=0;/eg"
0 at -e line 1.
  0 at -e line 1.
1 at -e line 1.
  0 at -e line 1.
2 at -e line 1.
  0 at -e line 1.
3 at -e line 1.
  0 at -e line 1.
4 at -e line 1.
  0 at -e line 1.
5 at -e line 1.
  0 at -e line 1.