---
name: "Debug::Trace"
section: "3pm"
platform: "linux"
package: "libdebug-trace-perl"
version: "0.05-3"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/Debug::Trace"
---

# Debug::Trace(3pm)

Perl extension to trace subroutine calls

## NAME

Debug::Trace - Perl extension to trace subroutine calls

## SYNOPSIS

```
  perl -MDebug::Trace=foo,bar yourprogram.pl
```

## DESCRIPTION

Debug::Trace instruments subroutines to provide tracing information upon every call and return.

Using Debug::Trace does not require any changes to your sources. Most often, it will be used from the command line:

```
  perl -MDebug::Trace=foo,bar yourprogram.pl
```

This will have your subroutines **foo()** and **bar()** printing call and return information.

Subroutine names may be fully qualified to denote subroutines in other packages than the default main::.

By default, the trace information is output using the standard **warn()** function.

### MODIFIERS

Modifiers can be inserted in the list of subroutines to change the default behavior of this module. All modifiers can be used in three ways:

- •

  `":"`*name* to enable a specific feature.

- •

  `":no"`*name* to disable a specific feature.

- •

  `":"`*name*`"("`*value*`")"` to set a feature to a specific value. In general, `":"`*name* is equivalent to `":"`*name*`"(1)"`, while `":no"`*name* corresponds to `":"`*name*`"(0)"`.

The following modifiers are recognized:

- :warn

  Uses **warn()** to produce the trace output (default). `":nowarn"` Sends trace output directly to STDERR.

- :caller

  Add basic call information to the trace message, including from where the routine was called, and by whom. This is enabled by default.

- :stacktrace

  Add a stack trace (call history).

- :maxlen(*length*)

  Truncate the length of the lines of trace information to *length* characters.

The following modifiers can be used to control the way Data::Dumper prints the values of parameters and return values. See also Data::Dumper.

- :indent

  Controls the style of indentation. It can be set to 0, 1, 2 or 3. Style 0 spews output without any newlines, indentation, or spaces between list items. `:indent(0)` is the default.

- :useqq

  When enabled, uses double quotes for representing string values. Whitespace other than space will be represented as `"[\n\t\r]"`, "unsafe" characters will be backslashed, and unprintable characters will be output as quoted octal integers. This is the default, use `":nouseqq"` to disable.

- :maxdepth(*depth*)

  Can be set to a positive integer that specifies the depth beyond which which we don't print structure contents. The default is 2, which means one level of array/hashes in argument lists and return values is expanded. If you use `":nomaxdepth"` or `:maxdepth(0)`, nested structures are fully expanded.

- :quotekeys

  Controls wether hash keys are always printed quoted. The default is `":noquotekeys"`.

- sortkeys

  Controls whether hash keys are dumped in sorted order. The default is `":nosortkeys"`.

Modifiers apply only to the subroutines that follow in the list of arguments.

## METHODS

None, actually. Everything is handled by the module's import.

## ENVIRONMENT VARIABLES

Environment variable `"PERL5DEBUGTRACE"` can be used to preset initial modifiers, e.g.:

```
    export PERL5DEBUGTRACE=":warn:indent(2):nomaxdepth:quotekeys"
```

## SEE ALSO

Data::Dumper, Carp

## AUTHOR

Jan-Pieter Cornet \<jpc@cpan.org\>; Jos Boumans \<kane@cpan.org\>; Johan Vromans \<jv@cpan.org\>;

This is an Amsterdam.pm production. See http://amsterdam.pm.org.

Current maintainer is Johan Vromans \<jv@cpan.org\>.

## COPYRIGHT

Copyright 2002,2013 Amsterdam.pm. All rights reserved.

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