I have a Perl/Tk program running under Windows that wants to spawn a copy of excel. Running `start file.csv` with backticks is usually the easiest way to do it, but with the Tk event loop running there's always a 30 second delay until the subprocess starts up. Task manager doesn't show any activity on the computer's part, and the backticks run quite snappily outside of Tk.

Anybody seen this before or have any ideas?

Here's a demo script. Use the menu option File/Report extract to see the pause. (Note that the window it opens is tiny, you might miss it on your screen). 

use Tk;
use File::Spec;

$top = MainWindow->new();

my $menubar = $top->Menu(-type => 'menubar');
$top->configure(-menu => $menubar);

my $filemenu = $menubar->cascade(-label => '~File', -tearoff => 0);
$filemenu->command(-label => '~Report extract',        
                   -command => [\&report_extract],
                   );

$filemenu->command(-label => 'E~xit',        
                   -command => [sub {exit}],
                   );
print STDERR "there's a tiny window open, it's small but it's there\n"
+;
MainLoop();   

sub report_extract {
   my $tmpdir = File::Spec->tmpdir();

   open (F, ">$tmpdir\\xx.csv") || die $!;
   print F "aaa,bbb,ccc\nddd,eee,fff\n";
   close F;
   my $cmd = "start $tmpdir\\xx.csv";
   print STDERR "running $cmd\n";
   `$cmd`;
}

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In reply to subprocess delay on Windows with Perl/Tk by kgoess

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