Yep, the leading whitespace will, by default, be matched exactly. If perl6 detects heterogeneous whitespace, it will detab from the first heterogeneous character, assuming 8-spaced hard tabs extending from the margin.

And, yes, there will be a pragma to change that default behaviour in various ways (e.g. to 4-space tabs, full-detabbing, no-detabbing, etc. etc.).