Perl Nixpkgs provides a function buildPerlPackage, a generic package builder function for any Perl package that has a standard Makefile.PL. It’s implemented in pkgs/development/perl-modules/generic. Perl packages from CPAN are defined in pkgs/top-level/perl-packages.nix, rather than pkgs/all-packages.nix. Most Perl packages are so straight-forward to build that they are defined here directly, rather than having a separate function for each package called from perl-packages.nix. However, more complicated packages should be put in a separate file, typically in pkgs/development/perl-modules. Here is an example of the former: ClassC3 = buildPerlPackage rec { name = "Class-C3-0.21"; src = fetchurl { url = "mirror://cpan/authors/id/F/FL/FLORA/${name}.tar.gz"; sha256 = "1bl8z095y4js66pwxnm7s853pi9czala4sqc743fdlnk27kq94gz"; }; }; Note the use of mirror://cpan/, and the ${name} in the URL definition to ensure that the name attribute is consistent with the source that we’re actually downloading. Perl packages are made available in all-packages.nix through the variable perlPackages. For instance, if you have a package that needs ClassC3, you would typically write foo = import ../path/to/foo.nix { inherit stdenv fetchurl ...; inherit (perlPackages) ClassC3; }; in all-packages.nix. You can test building a Perl package as follows: $ nix-build -A perlPackages.ClassC3 buildPerlPackage adds perl- to the start of the name attribute, so the package above is actually called perl-Class-C3-0.21. So to install it, you can say: $ nix-env -i perl-Class-C3 (Of course you can also install using the attribute name: nix-env -i -A perlPackages.ClassC3.) So what does buildPerlPackage do? It does the following: In the configure phase, it calls perl Makefile.PL to generate a Makefile. You can set the variable makeMakerFlags to pass flags to Makefile.PL It adds the contents of the PERL5LIB environment variable to #! .../bin/perl line of Perl scripts as -Idir flags. This ensures that a script can find its dependencies. In the fixup phase, it writes the propagated build inputs (propagatedBuildInputs) to the file $out/nix-support/propagated-user-env-packages. nix-env recursively installs all packages listed in this file when you install a package that has it. This ensures that a Perl package can find its dependencies. buildPerlPackage is built on top of stdenv, so everything can be customised in the usual way. For instance, the BerkeleyDB module has a preConfigure hook to generate a configuration file used by Makefile.PL: { buildPerlPackage, fetchurl, db }: buildPerlPackage rec { name = "BerkeleyDB-0.36"; src = fetchurl { url = "mirror://cpan/authors/id/P/PM/PMQS/${name}.tar.gz"; sha256 = "07xf50riarb60l1h6m2dqmql8q5dij619712fsgw7ach04d8g3z1"; }; preConfigure = '' echo "LIB = ${db}/lib" > config.in echo "INCLUDE = ${db}/include" >> config.in ''; } Dependencies on other Perl packages can be specified in the buildInputs and propagatedBuildInputs attributes. If something is exclusively a build-time dependency, use buildInputs; if it’s (also) a runtime dependency, use propagatedBuildInputs. For instance, this builds a Perl module that has runtime dependencies on a bunch of other modules: ClassC3Componentised = buildPerlPackage rec { name = "Class-C3-Componentised-1.0004"; src = fetchurl { url = "mirror://cpan/authors/id/A/AS/ASH/${name}.tar.gz"; sha256 = "0xql73jkcdbq4q9m0b0rnca6nrlvf5hyzy8is0crdk65bynvs8q1"; }; propagatedBuildInputs = [ ClassC3 ClassInspector TestException MROCompat ]; };
Generation from CPAN Nix expressions for Perl packages can be generated (almost) automatically from CPAN. This is done by the program nix-generate-from-cpan, which can be installed as follows: $ nix-env -i nix-generate-from-cpan This program takes a Perl module name, looks it up on CPAN, fetches and unpacks the corresponding package, and prints a Nix expression on standard output. For example: $ nix-generate-from-cpan XML::Simple XMLSimple = buildPerlPackage rec { name = "XML-Simple-2.22"; src = fetchurl { url = "mirror://cpan/authors/id/G/GR/GRANTM/${name}.tar.gz"; sha256 = "b9450ef22ea9644ae5d6ada086dc4300fa105be050a2030ebd4efd28c198eb49"; }; propagatedBuildInputs = [ XMLNamespaceSupport XMLSAX XMLSAXExpat ]; meta = { description = "An API for simple XML files"; license = with stdenv.lib.licenses; [ artistic1 gpl1Plus ]; }; }; The output can be pasted into pkgs/top-level/perl-packages.nix or wherever else you need it.
Cross-compiling modules Nixpkgs has experimental support for cross-compiling Perl modules. In many cases, it will just work out of the box, even for modules with native extensions. Sometimes, however, the Makefile.PL for a module may (indirectly) import a native module. In that case, you will need to make a stub for that module that will satisfy the Makefile.PL and install it into lib/perl5/site_perl/cross_perl/${perl.version}. See the postInstall for DBI for an example.