First seven essential debugger commands s - single-step execute the next line, stepping into subroutines. n - single-step execute the next line, stepping over subroutines. r - non-stop execute until the return from the current subroutine c <line-number or subroutine> - non-stop execute until a particular line l <line-number, range, or subroutine> - list source-code. x <expression> - evaluate and pretty-print <expression> q - quit debugger