When you paste a block of text into a Putty window, many times you’ll get an increasing number of leading tabs. Not so if you use gnome-terminal (IIRC). Quite annoying in a Windows world.
Strip tabs and spaces out from current position to the end of the file with:
Or perhaps you only want a small block in the middle of the file changed. First, turn on line numbers.
` :set number `
Then search and replace on specific line numbers (in this example lines 15 through 41).
Then use Ctrl-V (down arrow or h,j,k,l keys to select block) and hit “>” to re-indent. Works much better than reformatting by hand.