Introduce a break-point function called `bp`, based on the tcl wiki's
minimal debugger.
```tcl
proc bp {{s {}}} {
if ![info exists ::bp_skip] {
set ::bp_skip [list]
} elseif {[lsearch -exact $::bp_skip $s]>=0} return
if [catch {info level -1} who] {set who ::}
while 1 {
puts -nonewline "$who/$s> "; flush stdout
gets stdin line
if {$line=="c"} {puts "continuing.."; break}
if {$line=="i"} {set line "info locals"}
catch {uplevel 1 $line} res
puts $res
}
}
```
```
... your test code before break-point
bp 1
... your test code after break-point
```
The `bp 1` will give back the tcl interpreter to the developer, and
allow you to interactively print local variables (through `puts`), run
functions and so forth.
Source: https://wiki.tcl-lang.org/page/A+minimal+debugger
---------
Signed-off-by: Kyle Kim <kimkyle@amazon.com>
Signed-off-by: Madelyn Olson <madelyneolson@gmail.com>
Co-authored-by: Madelyn Olson <madelyneolson@gmail.com>
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