[youngnh]

C-M-\ actually only indents the 'region', which is the text between the point (your cursor) and the mark (C-Space). The neat thing about this is that yank (C-y) automatically sets the point and the mark at opposite sides of the yanked text. After copying an expression written in the slime repl to a buffer, C-M-\ works without having to move your cursor to the beginning of the expression.

[dpapathanasiou]

Thanks for that clarification.

Actually, I don't use C-M-\ much, since I prefer to work in individual blocks and C-M-u-q does that nicely, without my worrying where I last set the mark.