NAME
   Devel::ebug - A simple, extensible Perl debugger

SYNOPSIS
     use Devel::ebug;
     my $ebug = Devel::ebug->new;
     $ebug->program("calc.pl");
     $ebug->load;

     print "At line: "       . $ebug->line       . "\n";
     print "In subroutine: " . $ebug->subroutine . "\n";
     print "In package: "    . $ebug->package    . "\n";
     print "In filename: "   . $ebug->filename   . "\n";
     print "Code: "          . $ebug->codeline   . "\n";
     $ebug->step;
     $ebug->step;
     $ebug->next;
     my($stdout, $stderr) = $ebug->output;
     $ebug->break_point(6);
     $ebug->break_point(6, '$e = 4');
     $ebug->break_point("t/Calc.pm", 29);
     $ebug->break_point("t/Calc.pm", 29, '$i == 2');
     $ebug->break_point_subroutine("main::add");
     $ebug->break_point_delete(29);
     $ebug->break_point_delete("t/Calc.pm", 29);
     my @filenames    = $ebug->filenames();
     my @break_points = $ebug->break_points();
     $ebug->watch_point('$x > 100');
     my $codelines = $ebug->codelines(@span);
     $ebug->run;
     my $pad  = $ebug->pad;
     foreach my $k (sort keys %$pad) {
       my $v = $pad->{$k};
       print "Variable: $k = $v\n";
     }
     my $v = $ebug->eval('2 ** $exp');
     my $y = $ebug->yaml('$z');
     my @frames = $ebug->stack_trace;
     my @frames2 = $ebug->stack_trace_human;
     $ebug->undo;
     $ebug->return;
     print "Finished!\n" if $ebug->finished;

DESCRIPTION
   A debugger is a computer program that is used to debug other programs.
   Devel::ebug is a simple, extensible Perl debugger with a clean API.
   Using this module, you may easily write a Perl debugger to debug your
   programs. Alternatively, it comes with an interactive debugger, ebug.

   perl5db.pl, Perl's current debugger is currently 2,600 lines of magic
   and special cases. The code is nearly unreadable: fixing bugs and adding
   new features is fraught with difficulties. The debugger has no test
   suite which has caused breakage with changes that couldn't be properly
   tested. It will also not debug regexes. Devel::ebug is aimed at fixing
   these problems and delivering a replacement debugger which provides a
   well-tested simple programmatic interface to debugging programs. This
   makes it easier to build debuggers on top of Devel::ebug, be they
   console-, curses-, GUI- or Ajax-based.

   There are currently two user interfaces to Devel::debug, ebug and
   ebug_http. ebug is a console-based interface to debugging programs, much
   like perl5db.pl. ebug_http is an innovative web-based interface to
   debugging programs.

   Note that if you're debugging a program, you can invoke the debugger in
   the program itself by using the INT signal:

     kill 2, $$ if $square > 100;

   Devel::ebug is a work in progress.

   Internally, Devel::ebug consists of two parts. The frontend is
   Devel::ebug, which you interact with. The frontend starts the code you
   are debugging in the background under the backend (running it under perl
   -d:ebug code.pl). The backend starts a TCP server, which the frontend
   then connects to, and uses this to drive the backend. This adds some
   flexibilty in the debugger. There is some minor security in the
   client/server startup (a secret word), and a random port is used from
   3141-4165 so that multiple debugging sessions can happen concurrently.

CONSTRUCTOR
 new
   The constructor creats a Devel::ebug object:

     my $ebug = Devel::ebug->new;

 program
   The program method selects which program to load:

     $ebug->program("calc.pl");

 load
   The load method loads the program and gets ready to debug it:

     $ebug->load;

METHODS
 break_point
   The break_point method sets a break point in a program. If you are
   run-ing through a program, the execution will stop at a break point.
   Break points can be set in a few ways.

   A break point can be set at a line number in the current file:

     $ebug->break_point(6);

   A break point can be set at a line number in the current file with a
   condition that must be true for execution to stop at the break point:

     $ebug->break_point(6, '$e = 4');

   A break point can be set at a line number in a file:

     $ebug->break_point("t/Calc.pm", 29);

   A break point can be set at a line number in a file with a condition
   that must be true for execution to stop at the break point:

     $ebug->break_point("t/Calc.pm", 29, '$i == 2');

 break_point_delete
   The break_point_delete method deletes an existing break point. A break
   point at a line number in the current file can be deleted:

     $ebug->break_point_delete(29);

   A break point at a line number in a file can be deleted:

     $ebug->break_point_delete("t/Calc.pm", 29);

 break_point_subroutine
   The break_point_subroutine method sets a break point in a program right
   at the beginning of the subroutine. The subroutine is specified with the
   full package name:

     $ebug->break_point_subroutine("main::add");
     $ebug->break_point_subroutine("Calc::fib");

 break_points
   The break_points method returns a list of all the line numbers in the
   current file that have a break point set.

     my @break_points = $ebug->break_points();

 codeline
   The codeline method returns the line of code that is just about to be
   executed:

     print "Code: "          . $ebug->codeline   . "\n";

 codelines
   The codelines method returns lines of code.

   It can return all the code lines in the current file:

     my @codelines = $ebug->codelines();

   It can return a span of code lines from the current file:

     my @codelines = $ebug->codelines(1, 3, 4, 5);

   It can return all the code lines in a file:

     my @codelines = $ebug->codelines("t/Calc.pm");

   It can return a span of code lines in a file:

     my @codelines = $ebug->codelines("t/Calc.pm", 5, 6);

 eval
   The eval method evaluates Perl code in the current program and returns
   the result:

     my $v = $ebug->eval('2 ** $exp');

 filename
   The filename method returns the filename of the currently running code:

     print "In filename: "   . $ebug->filename   . "\n";

 filenames
   The filenames method returns a list of the filenames of all the files
   currently loaded:

     my @filenames = $ebug->filenames();

 finished
   The finished method returns whether the program has finished running:

     print "Finished!\n" if $ebug->finished;

 line
   The line method returns the line number of the statement about to be
   executed:

     print "At line: "       . $ebug->line       . "\n";

 next
   The next method steps onto the next line in the program. It executes any
   subroutine calls but does not step through them.

     $ebug->next;

 output
   The output method returns any content the program has output to either
   standard output or standard error:

     my($stdout, $stderr) = $ebug->output;

 package
   The package method returns the package of the currently running code:

     print "In package: "    . $ebug->package    . "\n";

 pad
     my $pad  = $ebug->pad;
     foreach my $k (sort keys %$pad) {
       my $v = $pad->{$k};
       print "Variable: $k = $v\n";
     }

 return
   The return subroutine returns from a subroutine. It continues running
   the subroutine, then single steps when the program flow has exited the
   subroutine:

     $ebug->return;

   It can also return your own values from a subroutine, for testing
   purposes:

     $ebug->return(3.141);

 run
   The run subroutine starts executing the code. It will only stop on a
   break point or watch point.

     $ebug->run;

 step
   The step method steps onto the next line in the program. It steps
   through into any subroutine calls.

     $ebug->step;

 subroutine
   The subroutine method returns the subroutine of the currently working
   code:

     print "In subroutine: " . $ebug->subroutine . "\n";

 stack_trace
   The stack_trace method returns the current stack trace, using
   Devel::StackTrace. It returns a list of Devel::StackTraceFrame methods:

     my @frames = $ebug->stack_trace;
     foreach my $frame (@trace) {
       print $frame->package, "->",$frame->subroutine,
       "(", $frame->filename, "#", $frame->line, ")\n";
     }

 stack_trace_human
   The stack_trace_human method returns the current stack trace in a
   human-readable format:

     my @frames = $ebug->stack_trace_human;
     foreach my $frame (@trace) {
       print "$frame\n";
     }

 undo
   The undo method undos the last action. It accomplishes this by
   restarting the process and passing (almost) all the previous commands to
   it. Note that commands which do not change state are ignored. Commands
   that change state are: break_point, break_point_delete,
   break_point_subroutine, eval, next, step, return, run and watch_point.

     $ebug->undo;

   It can also undo multiple commands:

     $ebug->undo(3);

 watch_point
   The watch point method sets a watch point. A watch point has a
   condition, and the debugger will stop run-ing as soon as this condition
   is true:

     $ebug->watch_point('$x > 100');

 yaml
   The eval method evaluates Perl code in the current program and returns
   the result of YAML's Dump() method:

     my $y = $ebug->yaml('$z');

SEE ALSO
   perldebguts

BUGS
   Devel::ebug does not quite work under 5.8.0.

   Devel::ebug does not handle signals under Windows.

AUTHOR
   Leon Brocard, "<[email protected]>"

COPYRIGHT
   Copyright (C) 2005, Leon Brocard

   This module is free software; you can redistribute it or modify it under
   the same terms as Perl itself.

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