Programming Perl, 4th Edition

Stepping and Running

The debugger operates by stepping through your program line by line. The following commands let you control what you skip over and where you stop.

s [EXPR]

The s debugger command single-steps through the program. That is, the debugger will execute the next line of your program until another statement is reached, descending into subroutine calls as necessary. If the next line to execute involves a function call, then the debugger stops at the first line inside that function. If an EXPR is supplied that includes function calls, these will be single-stepped, too.

n [EXPR]

The n command executes subroutine calls, without stepping through them, until the beginning of the next statement at this same level (or higher). If an EXPR is supplied that includes function calls, those functions will be executed with stops before each statement.

<ENTER>

If you just hit enter at the debugger prompt, the previous n or s command is repeated.

.

The . command returns the internal debugger pointer to the line last executed and prints out that line.

r

This command continues until the currently executing subroutine returns. It displays the return value if the PrintRet option is set, which it is by default.