tcltk-depends is a debhelper-like program which is responsible for generating the ${libtclXY:Depends},
${libtkXY:Depends}, ${libtcl:Depends}, ${libtk:Depends}, ${tclXY:Depends}, ${tkXY:Depends},
${tcl:Depends} and ${tk:Depends} substitution variables and adding them to substvars files.
If you use this program, your package must build-depend on tcl-dev or tk-dev. If you use ${tclXY:Depends}
or ${tkXY:Depends} variables, your package must build-depend on tcl-dev (>= 8.6.0+7) or tk-dev (>=
8.6.0+7). If you use ${libtclXY:Depends}, ${libtkXY:Depends}, ${libtcl:Depends} or {libtk:Depends}
variables, your package must build-depend on tcl-dev (>= 8.6.0+9) or tk-dev (>= 8.6.0+9).