Programming Perl, 4th Edition

Breakpoints

b

b LINE

b CONDITION

b LINE CONDITION

b SUBNAME

b SUBNAME CONDITION

b postpone SUBNAME

b postpone SUBNAME CONDITION

b compile SUBNAME

b load FILENAME

The b debugger command sets a breakpoint before LINE, telling the debugger to stop the program at that point so that you can poke around. If LINE is omitted, it sets a breakpoint on the line that’s about to execute. If CONDITION is specified, it’s evaluated each time the statement is reached: a breakpoint is triggered only if CONDITION is true. Breakpoints may only be set on lines that begin an executable statement. Note that conditions don’t use if:

b 237 $x > 30
b 237 ++$count237 < 11
b 33 /pattern/i

The b SUBNAME form sets a (possibly conditional) breakpoint before the first line of the named subroutine. SUBNAME may be a variable containing a code reference; if so, CONDITION is not supported.

There are several ways to set a breakpoint on code that hasn’t even been compiled yet. The b postpone form sets a (possibly conditional) breakpoint at the first line of SUBNAME after it is compiled.

The b compile form sets a breakpoint on the first statement to be executed after SUBNAME is compiled. Note that, unlike the postpone form, this statement is outside the subroutine in question because the subroutine hasn’t been called yet, only compiled.

The b load form sets a breakpoint on the first executed line of the file. The FILENAME should be a full pathname as found in the %INC values.

d

d LINE

This command deletes the breakpoint at LINE; if omitted, ...