Allow the option SHEBANG=relocatable

Author: Salve J. Nilsen

lib/ExtUtils/MM_Any.pm

@@ -2373,7 +2373,7 @@ CODE
     $self->{UNINSTALL}   ||= $self->oneliner('uninstall', ["-MExtUtils::Command::MM"]);
     $self->{WARN_IF_OLD_PACKLIST} ||=
       $self->oneliner('warn_if_old_packlist', ["-MExtUtils::Command::MM"]);
-    $self->{FIXIN}       ||= $self->oneliner('MY->fixin(shift)', ["-MExtUtils::MY"]);
+    $self->{FIXIN}       ||= $self->oneliner('$ENV{PERL_MM_SHEBANG} ||= "$(SHEBANG)"; MY->fixin(shift)', ["-MExtUtils::MY"]);
     $self->{EQUALIZE_TIMESTAMP} ||= $self->oneliner('eqtime', ["-MExtUtils::Command"]);
 
     $self->{UNINST}     ||= 0;

lib/ExtUtils/MM_Unix.pm

@@ -415,6 +415,7 @@ sub constants {
               PERLRUNINST     FULLPERLRUNINST   ABSPERLRUNINST
               PERL_CORE
               PERM_DIR PERM_RW PERM_RWX
+              SHEBANG
 
 	      ) )
     {
@@ -1174,8 +1175,9 @@ WARNING
 
 Inserts the sharpbang or equivalent magic number to a set of @files.
 
-If the environment variable C<PERL_MM_FORCE_SHEBANG=relocatable> is set,
-then any found shebang/sharpbang lines are set to C<#!/usr/bin/env perl>.
+If the WriteMakefile option C<SHEBANG> is set to "relocatable", then any found
+shebang/sharpbang lines are set to C<#!/usr/bin/env perl> instead of the
+default perl.
 
 =cut
 
@@ -1251,8 +1253,17 @@ sub _fixin_replace_shebang {
 
     # Now look (in reverse) for interpreter in absolute PATH (unless perl).
     my $interpreter;
-    if ( defined $ENV{PERL_MM_FORCE_SHEBANG} && $ENV{PERL_MM_FORCE_SHEBANG} eq "relocatable" ) {
-        $interpreter = "/usr/bin/env perl";
+    if ( defined $ENV{PERL_MM_SHEBANG} ) {
+        if ( $ENV{PERL_MM_SHEBANG} eq "relocatable" ) {
+            $interpreter = "/usr/bin/env perl";
+            print "SHEBANG option set to 'relocatable': Changing shebang from '$cmd $arg' to '$interpreter'"
+                if $Verbose;
+            $arg = ""; # args don't work with /usr/bin/env perl
+        }
+        else {
+            print "SHEBANG option set to something other than 'relocatable': Ignoring it"
+                if $Verbose;
+        }
     }
     elsif ( $cmd =~ m{^perl(?:\z|[^a-z])} ) {
         if ( $Config{startperl} =~ m,^\#!.*/perl, ) {
@@ -1863,6 +1874,8 @@ EOP
 
     $self->{LIBPERL_A} ||= "libperl$self->{LIB_EXT}";
 
+    $self->{SHEBANG} ||= '';
+
     # make a simple check if we find strict
     warn "Warning: PERL_LIB ($self->{PERL_LIB}) seems not to be a perl library directory
         (strict.pm not found)"

lib/ExtUtils/MakeMaker.pm

@@ -113,6 +113,7 @@ my %Special_Sigs = (
  BUILD_REQUIRES     => 'HASH',
  CONFIGURE_REQUIRES => 'HASH',
  TEST_REQUIRES      => 'HASH',
+ SHEBANG            => '',
  SKIP               => 'ARRAY',
  TYPEMAPS           => 'ARRAY',
  XS                 => 'HASH',
@@ -325,6 +326,8 @@ sub full_setup {
 
     MACPERL_SRC MACPERL_LIB MACLIBS_68K MACLIBS_PPC MACLIBS_SC MACLIBS_MRC
     MACLIBS_ALL_68K MACLIBS_ALL_PPC MACLIBS_SHARED
+
+    SHEBANG
         /;
     push @attrib_help, @fs_macros;
     @macro_fsentity{@fs_macros, @dep_macros} = (1) x (@fs_macros+@dep_macros);
@@ -2785,6 +2788,16 @@ A minimal required perl version, if present, will look like this:
 
     perl(perl)>=5.008001
 
+=item SHEBANG
+
+When set to C<relocatable>, it makes C<ExtUtils::MM_Unix-E<gt>fixup()> change
+any shebang lines found (e.g. C<#!/usr/local/bin/perl>) into a relocatable
+version C<#!/usr/bin/env perl>. This is useful when writing tools that are
+intended to work seamlessly in different environments, eg. both in containers
+and with C<plenv(1)>.
+
+If C<SHEBANG> is set to anything else than C<relocatable>, it is ignored.
+
 =item SITEPREFIX
 
 Like PERLPREFIX, but only for the site install locations.
@@ -3374,14 +3387,6 @@ always return the default without waiting for user input.
 
 Same as the PERL_CORE parameter.  The parameter overrides this.
 
-=item PERL_MM_FORCE_SHEBANG
-
-When set to C<relocatable>, it makes C<ExtUtils::MM_Unix-E<gt>fixup()> change
-any shebang lines found (e.g. C<#!/usr/local/bin/perl>) into a relocatable
-version C<#!/usr/bin/env perl>. This is useful when writing tools that are
-intended to work seamlessly in different environments, eg. both in containers
-and with C<plenv(1)>.
-
 =back
 
 =head1 SEE ALSO