I have a main TCL proc that sources tons of other tcl procs in other folders and subsequent subdirectories. For example, in the main proc it has:
source $basepa
Perhaps a little more platform independent and using builtins commands instead of piping to a process:
foreach script [glob [file join $basepath folderA *.tcl]] {
source $script
}
Repeat for folderB.
If you have more stringent selection criteria, and don't worry about running on any other platforms, using find may be more flexible.