Gub - incomprehensible with comments

$ cat incomp.tcl

#! /bin/sh
# \
exec tclsh${TCL} "$0" "$@"


proc createGui {w compact} {

	set code [gub "

		# A row of labels over a row of entries
		# Use row/column adjustments to turn it
		# into a vertical stack of widgets.

		# This is understandable when working it out
		# but I'm not sure it can be easily understood
		# just by reading it.


		;L L L L			;# Four labels.
		;E E E E			;# Four entries.

		;Li				;# Another lable to show info.

		:Li -columnspan 4		;# Grid it to span all the columns.

		.{L} -text a b c d		;# Give the labels some text.

		# The power of Tcl!

		[expr {$compact ? {

			!:-L1-3		+2	;# Move labels L1-3 down by 2 rows
						;# relative to what would be their rows.

			!:-E0		-6	;# This pushes E0 down by 6 rows
						;# so it has to be pulled back up.

			!:-E1-3		+2	;# Entries E1-3 have to be pushed
						;# down like with L1-3.

			!:|L1-3,E1-3	-1	;# Pull back the columns for the widget by 1.
						;# This will put them all in column 0.


			.Li -text Compact
		} : {
			.Li -text Normal
		}}]
	" $w]

	eval $code

	puts $code
	puts ""
}


package require gub
namespace import ::gub::gub

package require Tk

toplevel .q

createGui .  no
createGui .q yes


# EOF


$ ./incomp.tcl

grid [ttk::label .l0 -text a] -row 0 -column 0
grid [ttk::label .l1 -text b] -row 0 -column 1
grid [ttk::label .l2 -text c] -row 0 -column 2
grid [ttk::label .l3 -text d] -row 0 -column 3
grid [ttk::entry .e0] -row 1 -column 0
grid [ttk::entry .e1] -row 1 -column 1
grid [ttk::entry .e2] -row 1 -column 2
grid [ttk::entry .e3] -row 1 -column 3
grid [ttk::label .l4 -text Normal] -columnspan 4 -row 2 -column 0

grid [ttk::label .q.l0 -text a] -row 0 -column 0
grid [ttk::label .q.l1 -text b] -row 2 -column 0
grid [ttk::label .q.l2 -text c] -row 4 -column 0
grid [ttk::label .q.l3 -text d] -row 6 -column 0
grid [ttk::entry .q.e0] -row 1 -column 0
grid [ttk::entry .q.e1] -row 3 -column 0
grid [ttk::entry .q.e2] -row 5 -column 0
grid [ttk::entry .q.e3] -row 7 -column 0
grid [ttk::label .q.l4 -text Compact] -columnspan 4 -row 8 -column 0