Some commonly used debug commands are:
* b [line number | function name]
create a breakpoint in a line or a function
* B [breakpoint number]
remove breakpoint
* l
list the content of the script
* L
list breakpoints
* n
step over subroutine
* s
single step
*
repeat the last n or s command
* p [variable name | statement ]
print the value of a variable or the result of a statement
* c
continue running till next breakpoint
* r
start to run
* q
quit the debugger
