Shell environment variables used by Perl 6

The variables you can declare to alter its behavior or gather additional information.

The behavior of Rakudo, the Perl 6 interpreter, can be tweaked by a (growing) number of environment variables; this section attempts to document all those currently in use. They are interpreter specific in all cases, except where some use conventional names such as PATH.

The underlying virtual machine is also sensitive to a series of environment variables; they are listed in this wiki page.

Module loading

RAKUDOLIB and PERL6LIB append a comma-delimited list of paths to the search list for modules. RAKUDOLIB is evaluated first.

If true, causes the module loader to print debugging information to standard error.

Error message verbosity and strictness

If present, the print_exception routine will use a class of that name to process the exception for output. Rakudo currently ships with Exceptions::JSON (invoked by setting this variable to JSON), to override the default output. NOTE: this env var was added in version 6.d. Early implementation has been available in Rakudo compiler as of version 2018.08, and before that it was available as RAKUDO_EXCEPTIONS_HANDLER.

If true, suppresses deprecation warnings triggered by the is DEPRECATED trait.

If true, deprecation warnings become thrown exceptions.

Displays source code in stack frames surrounded by the specified number of lines of context; for instance RAKUDO_VERBOSE_STACKFRAME = 1 will use one context line.

Controls whether .setting files are included in backtraces.

Affecting precompilation

When this is set, Rakudo will look for the standard repositories (perl, vendor, site) in the specified directory. This is intended as an escape hatch for build-time bootstrapping issues, where Rakudo may be built as an unprivileged user without write access to the runtime paths in NQP's config.

These are internal variables for passing serialized state to precompilation jobs in child processes. Please do not set them manually.

If set to 1, diagnostic information about the precompilation process is emitted.

Line editor

This specifies the preferred line editor to use; valid values are Readline, Linenoise, and none. A value of none is useful if you want to avoid the recommendation message upon REPL startup.

If set to 1, will disable multiline input for the REPL.

This specifies the location of the history file used by the line editor; the default is ~/.perl6/rakudo-history.


Is the default number of characters to read on an IO::Handle, defaults to 65536 (aka 64K).

Controls whether to emit ANSI codes for error highlighting. Defaults to true if unset, except on Windows.

Indicates the maximum number of threads used by default when creating a ThreadPoolScheduler. Defaults to 64.

The IO::Spec::Unix.tmpdir method will return $TMPDIR if it points to a directory with full access permissions for the current user, with a fallback default of '/tmp'.

IO::Spec::Cygwin and IO::Spec::Win32 use more Windows-appropriate lists which also include the %TEMP% and %TMP% environment variables.

The IO::Spec::Unix.path method splits $PATH as a shell would; i.e. as a colon-separated list. IO::Spec::Cygwin inherits this from IO::Spec::Unix. IO::Spec::Win32.path will read the first defined of either %PATH% or %Path% as a semicolon-delimited list.

Indicates the period in which the telemetry snapper will take a snapshot. Defaults to .1 for 10 snapshots per second.


Initial version written by the Rakudo contributors, see the CREDITS file.

The initial version of this manual page was written by Reini Urban, Moritz Lenz and the Rakudo contributors.