To the best of my knowledge, you cannot have two levels of shebang-activated programs. So if you run ./test.pl which starts with #!/some/program, then /some/program cannot also be a shebang program.

The solution (or at least a solution) is to call /usr/bin/env, which itself does shebang-emulation, instead of calling your wrapper directly.

/path/to/perlwrapper: 

#!/usr/bin/perl

print "wrapper about to execute @ARGV\n";
exec "/usr/bin/perl", @ARGV;

[download]
test.pl: 
#!/usr/bin/env /path/to/perlwrapper

print "hello world!\n";

[download]
And then executing ./test.pl should work (at least, it did for me). Changing all your scripts to use env in their shebang line is a pain (you cannot just repace /usr/bin/perl with your wrapper), but it's the only way you can emulate nested shebangs. Otherwise, you'd have to make this version-delegation wrapper into a compiled binary.

There are also further complications: It appears that if the shebang line doesn't contain the word "perl", then perl itself will try to emulate shebangs and start an infinite loop (re-invoking your version-delegation wrapper). So I got weird results when I first named it "wrapper" instead of "perlwrapper"...

blokhead

In reply to Re: Conditionally executing different versions of Perl by blokhead
in thread Conditionally executing different versions of Perl by suaveant

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