Algol68 support three styles of comments: 1) COMMENT ... COMMENT 2) CO ... CO 3) # ... # These can't be nested, although you can have things like COMMENT CO ... CO COMMENT as a whole comment because from `COMMENT' up to the next closer `COMMENT' is a single comment (duh.)

that's not the way to do it

algol68g doesn't seem to support them

the default TAB function `indent-for-tab-comment' already does the right thing (r) and also handles regions.