Specify shebang on project using Perl Module::Build - perl

Question

I'm packaging clusterssh to openSUSE and need to change default shebang from #!/usr/bin/env perl to #!/usr/bin/perl. clusterssh uses Module::Build.
I'll probably use the patch (as Debian package do), but I wonder easy usage for fix_shebang_line(#files) in RPM packaging.

Answer 1

It's already called during the building process.
Basically, uninstalled scripts should use #!/usr/bin/perl or #!perl, and the installation process should rewrite that to the point to the perl used to run the installer. That way, a script installed by /usr/bin/perl will use /usr/bin/perl, and a script installed using /home/ikegami/usr/perlbrew/perls/5.26.2t/bin/perl will use /home/ikegami/usr/perlbrew/perls/5.26.2t/bin/perl.
(This applies to both the Module::Build installer and the ExtUtils::MakeMaker installer.)
Note that the documentation for fix_shebang_line says it doesn't touch a shebang line of #!/usr/bin/env perl (because it's not recognized as invocation of perl), so simply patching the scripts to use #!/usr/bin/perl instead of #!/usr/bin/env perl does the trick.
With that change, the install-ready staging directory (blib) produced by ./Build will contain the edited files.
$ perl -e'CORE::say $^X'
/home/ikegami/usr/perlbrew/perls/5.26.2t/bin/perl
$ for fn in ccon crsh csftp cssh ctel; do printf '%-6s ' "$fn:"; head -n 1 "bin_PL/$fn"; done
ccon: #!/usr/bin/perl
crsh: #!/usr/bin/perl
csftp: #!/usr/bin/perl
cssh: #!/usr/bin/perl
ctel: #!/usr/bin/perl
$ perl Build.PL
Could not get valid metadata. Error is: ERROR: Missing required field 'dist_abstract' for metafile
Could not create MYMETA files
Creating new 'Build' script for 'App-ClusterSSH' version 'v4.13.203'
$ ./Build
Building App-ClusterSSH
Using perl binary: /home/ikegami/usr/perlbrew/perls/5.26.2t/bin/perl
Using perl version v5.26.2
Generating: /home/ikegami/tmp/clusterssh/bin_PL/cssh
Generating: /home/ikegami/tmp/clusterssh/bin_PL/csftp
Generating: /home/ikegami/tmp/clusterssh/bin_PL/ccon
Generating: /home/ikegami/tmp/clusterssh/bin_PL/crsh
Generating: /home/ikegami/tmp/clusterssh/bin_PL/ctel
Generating: /home/ikegami/tmp/clusterssh/bin_PL/clusterssh_bash_completion.dist
$ for fn in ccon crsh csftp cssh ctel; do printf '%-6s ' "$fn:"; head -n 1 "blib/script/$fn"; done
ccon: #!/home/ikegami/usr/perlbrew/perls/5.26.2t/bin/perl
crsh: #!/home/ikegami/usr/perlbrew/perls/5.26.2t/bin/perl
csftp: #!/home/ikegami/usr/perlbrew/perls/5.26.2t/bin/perl
cssh: #!/home/ikegami/usr/perlbrew/perls/5.26.2t/bin/perl
ctel: #!/home/ikegami/usr/perlbrew/perls/5.26.2t/bin/perl
I didn't bother running ./Build install, whose main task is to copy the files from the staging directory into their final locations. Besides, that part will need to be replaced by your package manager anyway (assuming you're simply placing the contents of the blib directory into your package).
If you somehow need to do it yourself, you could use the following:
find bin -type f \
-exec perl -i -pe'
s/^#!\S*perl\S*/#!$^X/ if $. == 1;
close ARGV if eof;
' {} +
Notes:
Use the perl you wish the scripts to use.
GNU tools assumed; adjust as necessary.
close ARGV if eof; resets the line number ($.) for each file.
eof is different than eof(), and only the former will work here.
The line breaks are optional and may be removed.