Imager::Probe - hot needle of inquiry for libraries

  require Imager::Probe;

  my %probe = 
    (
     # short name of what we're looking for (displayed to user)
     name => "FOO",
     # pkg-config lookup
     pkg => [ qw/name1 name2 name3/ ],
     # perl subs that probe for the library
     code => [ \&foo_probe1, \&foo_probe2 ],
     # or just: code => \&foo_probe,
     inccheck => sub { ... },
     libcheck => sub { ... },
     # search for this library if libcheck not supplied
     libbase => "foo",
     # library link time options, uses libbase to build options otherwise
     libopts => "-lfoo",
     # C code to check the library is sane
     testcode => "...",
     # header files needed
     testcodeheaders => [ "stdio.h", "foo.h" ],
    );
  my $result = Imager::Probe->probe(\%probe)
    or print "Foo library not found: ",Imager::Probe->error;

Does the probes that were hidden in Imager's Makefile.PL, pulled out so the file format libraries can be externalized.

The return value is either nothing if the probe fails, or a hash containing:

• INC - -I and other C options
• LIBS - -L, -l and other link-time options
• DEFINE - -D options, if any.

The possible values for the hash supplied to the probe() method are:

• pkg - an array of pkg-config names to probe for. If the pkg-config checks pass, inccheck and libcheck aren't used.
• inccheck - a code reference that checks if the supplied include directory contains the required header files.
• libcheck - a code reference that checks if the supplied library directory contains the required library files. Note: the Makefile.PL version of this was supplied all of the library file names instead.
• libbase - if inccheck is supplied, but libcheck isn't, then a libcheck that checks for liblibbase$Config{_a} and liblibbase.$Config{so} is created. If libopts isn't supplied then that can be synthesized as -l<libbase>.
• libopts - if the libraries are found via inccheck/libcheck, these are the -l options to supply during the link phase.
• code - a code reference to perform custom checks. Returns the probe result directly. Can also be an array ref of functions to call.
• testcode - test C code that is run with Devel::CheckLib. You also need to set testcodeheaders.
• testcodeprologue - C code to insert between the headers and the main function.
• incpath - $Config{path_sep} separated list of header file directories to check, or a reference to an array of such.
• libpath - $Config{path_sep} separated list of library file directories to check, or a reference to an array of such.