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App::plx - Perl Layout Executor


  plx --help                             # This output

  plx --init <perl>                      # Initialize layout config
  plx --perl                             # Show layout perl binary
  plx --libs                             # Show layout $PERL5LIB entries
  plx --paths                            # Show layout additional $PATH entries
  plx --env                              # Show layout env var changes
  plx --cpanm -llocal --installdeps .    # Run cpanm from outside $PATH
  plx perl <args>                        # Run perl within layout
  plx -E '...'                           # (ditto)
  plx script-in-dev <args>               # Run dev/ script within layout
  plx script-in-bin <args>               # Run bin/ script within layout
  plx ./script <args>                    # Run script within layout
  plx script/in/cwd <args>               # (ditto)
  plx program <args>                     # Run program from layout $PATH


While perl has many tools for configuring per-project development environments, using them can still be a little on the lumpy side. With Carton, you find yourself running one of

  perl -Ilocal/lib/perl -Ilib bin/myapp
  carton exec perl -Ilib bin/myapp

With App::perlbrew,

  perlbrew switch perl-5.28.0@libname
  perl -Ilib bin/myapp


  plenv exec perl -Ilib bin/myapp

and if you have more than one distinct layer of dependencies, while local::lib will happily handle that, integrating it with everything else becomes a pain in the buttocks.

As a result of this, your not-so-humble author found himself regularly having a miniature perl executor script at the root of git clones that looked something like:

  eval $(perl -Mlocal::lib=--deactivate-all)
  export PERL5LIB=$PWD/local/lib/perl5
  ~/perl5/perlbrew/perls/perl-5.28.0/bin/$bin "$@"

and then running:

  ./pl perl -Ilib bin/myapp

However, much like back in 2007 frustration with explaining to other developers how to set up CPAN to install into ~/perl5 and how to set up one's environment variables to then find the modules so installed led to the exercise in rage driven development that first created local::lib, walking newbies through the creation and subsequent use of such a script was not the most enjoyable experience for anybody involved.

Thus, the creation of this module to reduce the setup process to:

  cpanm App::plx
  cd MyProject
  plx --init 5.28.0
  plx --cpanm -llocal --notest --installdeps .

Follwed by being able to immediately (and even more concisely) run:

  plx myapp

which will execute perl -Ilib bin/myapp with the correct perl and the relevant local::lib already in scope.

If this seems of use to you, the "QUICKSTART" is next and the "ACTIONS" section of this document lists the full capabilities of plx. Onwards!


Let's assume we're going to be working on Foo-Bar, so we start with:

  git clone
  cd Foo-Bar

Assuming the perl we'd get from running just perl suffices, then we next run:

  plx --init

If we want a different perl - say, we have a perl5.30.1 in our path, or a perl-5.30.1 built in perlbrew, we'd instead run:

  plx --init 5.30.1

To quickly get our dependencies available, we then run:

  plx --cpanm -llocal --notest --installdeps .

If the project is designed to use Carton and has a cpanfile.snapshot, instead we would run:

  plx --cpanm -ldevel --notest Carton
  plx carton install

If the goal is to test this against our current development version of another library, then we'd also want to run:

  plx --config libspec add 40otherlib.dir ../Other-Lib/lib

If we want our ~/perl local::lib available within the plx environment, we can add that as the least significant libspec with:

  plx --config libspec add 00tilde.ll $HOME/perl5

At which point, we're ready to go, and can run:

  plx myapp              # to run bin/myapp
  plx t/foo.t            # to run one test file
  plx prove              # to run all t/*.t test files
  plx -E 'say for @INC'  # to run a one liner within the layout

To learn everything else plx is capable of, read on to the "ACTIONS" section coming next.

Have fun!


Under normal circumstances, one would run something like:

  cpanm App::plx

However, if you want a self-contained plx script without having a cpan installer available, you can run:

  mkdir bin
  wget -O bin/plx

to get the current latest packed version.

The packed version bundles local::lib and File::Which, and also includes a modified --cpanm action that uses an inline App::cpanminus.


plx actions that execute external commands all clear any existing environment variables that start with PERL to keep an encapsulated setup for commands being run within the layouts - and also set PERL5OPT to exclude site_perl (but not vendor_perl) to avoid locally installed modules causing unexpected effects.

Having done so, plx then loads each env config entry and sets those variables - then prepends the plx specific entries to both PATH and PERL5LIB. You can add env config entries with "--config":

  plx --config env add NAME VALUE

The changes that will be made to your environment can be output by calling the "--env" command.

Additionally, environment variable overrides may be provided to the "--cmd", "--exec" and "--perl" commands by providing them in NAME=VALUE format:

  # do not do this, it will be deleted
  PERL_RL=Perl5 plx <something>

  # do this instead, it will provide the environment variable to the command
  plx PERL_RL=Perl5 <something>


  plx --help                             # Print synopsis
  plx --version                          # Print plx version

  plx --init <perl>                      # Initialize layout config for .
  plx --bareinit <perl>                  # Initialize bare layout config for .
  plx --base                             # Show layout base dir 
  plx --base <base> <action> <args>      # Run action with specified base dir
  plx --perl                             # Show layout perl binary
  plx --libs                             # Show layout $PERL5LIB entries
  plx --paths                            # Show layout additional $PATH entries
  plx --env                              # Show layout env var changes
  plx --cpanm -llocal --installdeps .    # Run cpanm from outside $PATH

  plx --config perl                      # Show perl binary
  plx --config perl set /path/to/perl    # Select exact perl binary
  plx --config perl set perl-5.xx.y      # Select perl via $PATH or perlbrew

  plx --config libspec                   # Show lib specifications
  plx --config libspec add <name> <path> # Add lib specification
  plx --config libspec del <name> <path> # Delete lib specification
  plx --config env                       # Show additional env vars
  plx --config env add <name> <path>     # Add env var
  plx --config env del <name> <path>     # Delete env var

  plx --exec <cmd> <args>                # exec()s with env vars set
  plx --perl <args>                      # Run perl with args

  plx --cmd <cmd> <args>                 # DWIM command:
    cmd = perl           -> --perl <args>
    cmd = -<flag>        -> --perl -<flag> <args>
    cmd = some/file      -> --perl some/file <args>
    cmd = ./file         -> --perl ./file <args>
    cmd = name ->
      exists .plx/cmd/<name> -> --perl .plx/cmd/<name> <args>
      exists dev/<name>      -> --perl dev/<name> <args>
      exists bin/<name>      -> --perl bin/<name> <args>
      else                   -> --exec <name> <args>

  plx --which <cmd>                      # Expands --cmd <cmd> without running
  plx <something> <args>                 # Shorthand for plx --cmd
  plx --commands <filter>?               # List available commands
  plx --multi [ <cmd1> <args1> ] [ ... ] # Run multiple actions
  plx --showmulti [ ... ] [ ... ]        # Show multiple action running
  plx [ ... ] [ ... ]                    # Shorthand for plx --multi
  plx --userinit <perl>                  # Init ~/.plx with ~/perl5 ll
  plx --installself                      # Installs plx and cpanm into layout
  plx --installenv                       # Appends plx --env call to .bashrc
  plx --userstrap <perl>                 # userinit+installself+installenv


Prints out the usage information (i.e. the "SYNOPSIS") for plx.


  plx --init                     # resolve 'perl' in $PATH
  plx --init perl                # (ditto)
  plx --init 5.28.0              # looks for perl5.28.0 in $PATH
                                 # or perl-5.28.0 in perlbrew
  plx --init /path/to/some/perl  # uses the absolute path directly

Initializes the layout.

If a perl name is passed, attempts to resolve it via $PATH and perlbrew and sets the result as the layout perl; if not looks for just perl.

Creates the following libspec config:

  25-local.ll  local
  50-devel.ll  devel
  75-lib.dir   lib


Identical to --init but creates no default configs except for perl.


  plx --base
  plx --base <base> <action> <args>

Without arguments, shows the selected base dir - plx finds this by checking for a .plx directory in the current directory, and if not tries the parent directory, recursively. The search stops either when plx finds a .git directory, to avoid accidentally escaping a project repository, or at the last directory before the root - i.e. plx will test /home but not /.

With arguments, specifies a base dir to use, and then invokes the rest of the arguments with that base dir selected - so for example one can make a default configuration in $HOME available as plh by running:

  plx --init $HOME
  alias plh='plx --base $HOME'


Prints the directories that will be added to PERL5LIB, one per line.

These will include the lib/perl5 subdirectory for each ll entry in the libspecs, and the directory for each dir entry.


Prints the directories that will be added to PATH, one per line.

These will include the containing directory of the environment's perl binary if not already in PATH, followed by the bin directories of any ll entries in the libspecs.


Prints the changes that will be made to your environment variables, in a syntax that is (hopefully) correct for your current shell.


  plx --cpanm -Llocal --installdeps .
  plx --cpanm -ldevel App::Ack

Finds the cpanm binary in the PATH that plx was executed from, and executes it using the layout's perl binary and environment variables.

Requires the user to specify a local::lib to install into via -l or -L in order to avoid installing modules into unexpected places.

Note that this action exists primarily for bootstrapping, and if you want to use a different installer such as App::cpm, you'd install it with:

  plx --cpanm -ldevel App::cpm

and then subsequently run e.g.

  plx cpm install App::Ack

to install modules.


  plx --exec <command> <args>

Sets up the layout's environment variables and execs the command.


  plx --perl
  plx --perl <options> <script> <args>

Without arguments, sugar for --config perl.

Otherwise, sets up the layout's environment variables and execs the layout's perl with the given options and arguments.


  plx --cmd <cmd> <args>
    cmd = perl           -> --perl <args>
    cmd = -<flag>        -> --perl -<flag> <args>
    cmd = some/file      -> --perl some/file <args>
    cmd = ./file         -> --perl ./file <args>
    cmd = name ->
      exists .plx/cmd/<name> -> --perl .plx/cmd/<name> <args>
      exists dev/<name>      -> --perl dev/<name> <args>
      exists bin/<name>      -> --perl bin/<name> <args>
      else                   -> --exec <name> <args>

Note: Much like the devel local::lib is created to allow for the installation of out-of-band dependencies that aren't going to be needed in production, the dev directory is supported to allow for the easy addition of development time only sugar commands. Note that since perl will re-exec anything with a non-perl shebang, one can add wrappers here ala:

  $ cat dev/prove
  exec prove -j8 "$@"


  plx --which <cmd>

Outputs the expanded form of a --cmd invocation without running it.


  plx --config                     # Show current config
  plx --config <name>              # Show current <name> config
  plx --config <name> <operation>  # Invoke config operation


  plx --config perl
  plx --config perl set <spec>

If the spec passed to set contains a / character, plx assumes that it's an absolute bath and records it as-is.

If not, we go a-hunting.

First, if the spec begins with a 5, we replace it with perl5.

Second, we search $PATH for a binary of that name, and record it if so.

Third, if the (current) spec begins perl5, we replace it with perl-5.

Fourth, we search $PATH for a perlbrew binary, and ask it if it has a perl named after the spec, and record that if so.

Fifth, we shrug and hope the user can come up with an absolute path next time.

Note: The original spec passed to set is recorded in .plx/perl.spec, so if you intend to share the .plx directory across multiple machines via version control or otherwise, remove/exclude the .plx/perl file and plx will automatically attempt to re-locate the perl on first invocation.


  plx --config libspec
  plx --config libspec add <name> <spec>
  plx --config libspec del <name> <spec>

A libspec config entry consists of a name and a spec, and the show output prints them space separated one per line, with enough spaces to make the specs align:

  25-local.ll  local
  50-devel.ll  devel
  75-lib.dir   lib

The part of the name before the last . is not semantically significant to plx, but is used for asciibetical sorting of the libspec entries to determine in which order to apply them.

The part after must be either ll for a local::lib, or dir for a bare lib directory.

When loaded, the spec is (if relative) resolved to an absolute path relative to the layout root, then all .. entries and symlinks resolved to give a final path used to set up the layout environment.


  plx --config env
  plx --config env add <name> <value>
  plx --config env del <name> <value>

Manages additional environment variables, which are set immediately before any environment changes required for the current "libspec" and "perl" settings are processed.


  plx --commands         # all commands
  plx --commands c       # all commands starting with c
  plx --commands /json/  # all commands matching /json/

Lists available commands, name first, then full path.

If a filter argument is given, treats it as a fixed prefix to filter the command list, unless the filter is /re/ in which case the slashes are stripped and the filter is treated as a regexp.


  plx --multi [ --init ] [ --config perl set 5.28.0 ]

Runs multiple plx commands from a single invocation delimited by [ ... ].


  plx --showmulti [ --init ] [ --config perl set 5.28.0 ]

Outputs approximate plx invocations that would be run by --multi.


Same as --init but assumes $HOME as base and sets up only a single libspec pointing at $HOME/perl5.


Installs App::plx and App::cpanminus into the highest-numbered local::lib within the layout.


(bash only currently)

Appends an eval line to set up the layout environment to the user's bashrc.


Convenience command for --userinit plus --installself plus --installenv.


 mst - Matt S. Trout (cpan:MSTROUT) <>


None yet - maybe this software is perfect! (ahahahahahahahahaha)


Copyright (c) 2020 the App::plx "AUTHOR" and "CONTRIBUTORS" as listed above.


This library is free software and may be distributed under the same terms as perl itself.