Re: using 'use' conditionally

[xafwodahs]

Here is a test script. Run it with a -g as the first parameter.

On a machine without Tk, it will correctly die.
On a machine with Tk, it *should* bring up a simple Tk window, but it exits instead. If I replace the 'require' and 'import' with the 'use', then it works.

if ($ARGV[0] =~ /-g/) {
   # do gui
   
   die "You need Tk." unless (eval("require Tk;"));

   #use Tk;
   require Tk;
   Tk->import;

   $mw = MainWindow->new;
   $mw->Button(-text=>"EXIT",
               -command=>sub{exit})->pack(-side=>"bottom",
                                          -fill=>"both");
   MainLoop;

   print "gui done.\n";

} else {
   # do non-gui

   print "non-gui stuff\n";
}

[tye]

Change MainLoop; to MainLoop(); to fix the problem. MainLoop; is only the same as MainLoop(); if, at the time that it is compiled, you have already declared a subroutine with that name. Otherwise it is a bareword which is either the same as "MainLoop"; (if strict isn't on) or is a fatal error.

Read (tye)Re: use vs. require and Conditional compile-time magic (RE: Checking to see if a particular Module is installed) for more to meditate on.

Thanks to ybiC for pointing this out.

        - tye