A perl snippet to replace tabs by spaces, but the ‘right’ way, inserting enough spaces to bring the text up to the nth column.

The regular expression to do this is:

s/\t/" "x(8-(length($&)%8))/eg

To detab every file in this tree, recursively:

grep "\\t" -lr | xargs perl -pi -e 's/\t/" "x(8-(length($)%8))/eg'