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Dave Rolsky > Devel-StackTrace > Devel::StackTrace



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Module Version: 2.03   Source  


Devel::StackTrace - An object representing a stack trace


version 2.03


  use Devel::StackTrace;

  my $trace = Devel::StackTrace->new;

  print $trace->as_string; # like carp

  # from top (most recent) of stack to bottom.
  while ( my $frame = $trace->next_frame ) {
      print "Has args\n" if $frame->hasargs;

  # from bottom (least recent) of stack to top.
  while ( my $frame = $trace->prev_frame ) {
      print "Sub: ", $frame->subroutine, "\n";


The Devel::StackTrace module contains two classes, Devel::StackTrace and Devel::StackTrace::Frame. These objects encapsulate the information that can retrieved via Perl's caller function, as well as providing a simple interface to this data.

The Devel::StackTrace object contains a set of Devel::StackTrace::Frame objects, one for each level of the stack. The frames contain all the data available from caller.

This code was created to support my Exception::Class::Base class (part of Exception::Class) but may be useful in other contexts.


When describing the methods of the trace object, I use the words 'top' and 'bottom'. In this context, the 'top' frame on the stack is the most recent frame and the 'bottom' is the least recent.

Here's an example:

  foo();  # bottom frame is here

  sub foo {

  sub bar {
     Devel::StackTrace->new;  # top frame is here.


This class provide the following methods:


Returns a new Devel::StackTrace object.

Takes the following parameters:


Returns the next Devel::StackTrace::Frame object on the stack, going down. If this method hasn't been called before it returns the first frame. It returns undef when it reaches the bottom of the stack and then resets its pointer so the next call to $trace->next_frame or $trace->prev_frame will work properly.


Returns the next Devel::StackTrace::Frame object on the stack, going up. If this method hasn't been called before it returns the last frame. It returns undef when it reaches the top of the stack and then resets its pointer so the next call to $trace->next_frame or $trace->prev_frame will work properly.


Resets the pointer so that the next call to $trace->next_frame or $trace->prev_frame will start at the top or bottom of the stack, as appropriate.


When this method is called with no arguments, it returns a list of Devel::StackTrace::Frame objects. They are returned in order from top (most recent) to bottom.

This method can also be used to set the object's frames if you pass it a list of Devel::StackTrace::Frame objects.

This is useful if you want to filter the list of frames in ways that are more complex than can be handled by the $trace->filter_frames method:

  $stacktrace->frames( my_filter( $stacktrace->frames ) );


Given an index, this method returns the relevant frame, or undef if there is no frame at that index. The index is exactly like a Perl array. The first frame is 0 and negative indexes are allowed.


Returns the number of frames in the trace object.


Calls $frame->as_string on each frame from top to bottom, producing output quite similar to the Carp module's cluck/confess methods.

The optional \%p parameter only has one option. The max_arg_length parameter truncates each subroutine argument's string representation if it is longer than this number of characters.

If all the frames in a trace are skipped then this just returns the message passed to the constructor or the string "Trace begun".


Returns the message passed to the constructor. If this wasn't passed then this method returns undef.


Bugs may be submitted at

I am also usually active on IRC as 'autarch' on irc://


The source code repository for Devel-StackTrace can be found at


If you'd like to thank me for the work I've done on this module, please consider making a "donation" to me via PayPal. I spend a lot of free time creating free software, and would appreciate any support you'd care to offer.

Please note that I am not suggesting that you must do this in order for me to continue working on this particular software. I will continue to do so, inasmuch as I have in the past, for as long as it interests me.

Similarly, a donation made in this way will probably not make me work on this software much more, unless I get so many donations that I can consider working on free software full time (let's all have a chuckle at that together).

To donate, log into PayPal and send money to, or use the button at


Dave Rolsky <>



This software is Copyright (c) 2000 - 2017 by David Rolsky.

This is free software, licensed under:

  The Artistic License 2.0 (GPL Compatible)

The full text of the license can be found in the LICENSE file included with this distribution.

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