@node ax_sys_perlsharpbang
@unnumberedsec ax_sys_perlsharpbang

@majorheading Synopsis

@smallexample
AX_SYS_PERLSHARPBANG
@end smallexample

@majorheading Description

Determine how the perl interpreter is located by the OS kernel and make
substitution variable PERL_SHEBANG available. Does AC_PATH_PROG to find
the path to perl. As a side-effect, that sets PERLINTERP and makes it
available as a substitution variable.

Note: The macro allows for the possibility (expected to be seldom used)
of an explicit user override (the "user" being the operator executing
the final 'configure' script, in this context) by making the option
argument like:

@smallexample
  --with-perl-shebang='#! /my/funky/perlpath' # OR
  --with-perl-shebang='/my/funky/perlpath'  # we just throw away the #! anyway
                                            # bec it must be absent in Makefile
@end smallexample

Rationale: The are various ways of starting an interpreter on different
*nix-like systems. Many use the simple

@smallexample
  #!/usr/bin/perl
@end smallexample

but it could be instead

@smallexample
  #!/usr/local/bin/perl
@end smallexample

and there is even the possibility that the user wants

@smallexample
  #!/usr/bin/env perl
@end smallexample

to find whichever perl comes first in the current $PATH. This is
preferred by some of us because we run multiple perl installations on
the same box. Adjusting our $PATH then allows us to set precedence over
other perls, even whatever the "house" version is.

Users on very non-unix systems like MS Windows do not have a kernel that
does this kind of thing from the first line of script files, but instead
the perl on their machine is started and merely notices whatever comes
after the interpreter path on this first line of the script (options
like "-w").

Acknowledgement: this macro was in part inspired by Dean Povey's
AC_PROG_PERL_VERSION.

@majorheading Source Code

Download the
@uref{http://git.savannah.gnu.org/gitweb/?p=autoconf-archive.git;a=blob_plain;f=m4/ax_sys_perlsharpbang.m4,latest
version of @file{ax_sys_perlsharpbang.m4}} or browse
@uref{http://git.savannah.gnu.org/gitweb/?p=autoconf-archive.git;a=history;f=m4/ax_sys_perlsharpbang.m4,the
macro's revision history}.

@majorheading License

@w{Copyright @copyright{} 2009 Soren Andersen @email{somian@@pobox.com}}

Copying and distribution of this file, with or without modification, are
permitted in any medium without royalty provided the copyright notice
and this notice are preserved. This file is offered as-is, without any
warranty.