I have two scripts, alpha and beta:
alpha:
#! /tmp/beta
12345
abcde

[download]
beta:
#! /usr/bin/perl -wln
print scalar reverse if $. > 1;

[download]
(The real beta is much more complex.) I hoped that alpha would print:
    54321
    edcba

[download]
What actually printed:
    ./alpha: line 2: 12345: command not found
    ./alpha: line 3: abcde: command not found

[download]
"man execve" says that you can't have an interpreter running an interpreter, at least on Red Hat:
execve() executes the program pointed to by filename. filename must be either a binary executable, or a script starting with a line of the form "#! interpreter [arg]". In the latter case, the interpreter must be a valid pathname for an executable which is not itself a script,
It seems that Perl was invoked with alpha as an argument, noticed that the #! line didn't mention perl, and helpfully invoked a shell to interpret alpha. Well, heck—what can I do? I want alpha to remain unchanged. Am I forced to write beta in a compiled language? I want to use Perl, of course!

In reply to Nested #! interpreters by Neutron Jack

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