This business falls into the "well that's handy" followed by the "who in the world thought honoring continuation characters in comments was a good idea?!"
#! /bin/sh
# the next line restarts using tclsh \
exec tclsh "$0" ${1+"$@"}
And the nice thing about TCL as a language is there's just like 3 or 4 rules to remember and then you can embed the parser in your head. # is a command that discards all its arguments. So it's in the normal flow of syntax, so line continuation works. It's odd to see but easy to reason about after you are used to it.
https://wiki.tcl-lang.org/page/comment
with an especial nod toward: