How can I run through a Perl program step by step?

Question

I have a Perl program written by someone else. When I run it, it silently exits without writing anything to the logfile. Is there a way I can run this Perl program step by step, line by line by the interpreter and thus get to see where it terminates?

Answer 1

Yes, there is the Perl debugger which you can invoke with perl -d .

Documentation can be found in perldoc perldebug and perldoc perldebtut .

Probably the most useful commands would be:

s                 - step into current line.
n                 - step over current line.
r                 - step out of current function.
p <expr>          - print the expression.
b <line|subnm>    - sets a breakpoint
T                 - produce a stack trace.
c [<line|subnm>]  - continue running with optional one-time breakpoint.
h                 - help (for other commands).

Answer 2

There is a Perl module called "ptkdb" which is a standalone Perl interactive debugger. It works using the Tcl/Tk GUI, so you'll need that, too.

Depending on your OS you'll need to add some required modules .

Invoke it using

perl -d:ptkdb <your script>

If running some Unix/Linux system, you also need an X server.

Answer 3

Hachi has the answer. Use the Perl debugger by running perl with the -d flag. For information on how to use the debugger past starting it, see the Perl Debugging Tutorial .

Answer 4

There are two ways. The first is the one which Hachi and llioin already gave which is using the command-line switch "-d".

Or use an IDE . I am tried and used Komodo IDE which works like charm.