Perl/Tk menubar quirks - perl

Question

I'm trying to add a menubar with the standard File Open, Save and New options.
However, instead of behaving as expected, the subroutine handling the open, save and new actions is launched upon creation of the frame. But, when I actually click on them, it is not.
Following is the code I'm using. (Main window contains only the menubar)
#!/usr/bin/perl
use strict;
use warnings;
use diagnostics;
use Data::Dumper;
use Tk 8.0;
use Tk::NoteBook;
use Tk::MsgBox;
my $mw=MainWindow->new;
$mw->geometry("+500+300");
# Menu Bar Buttons
my $mbar=$mw->Menu();
$mw->configure(-menu => $mbar);
my $file=$mbar->cascade(-label=>"~File", -tearoff => 0);
my $help=$mbar->cascade(-label =>"~Help", -tearoff => 0);
# File Menu
$file->command(-label =>'~New ', -command=>&menu_file('n'), -accelerator=>'Ctrl+N');
$file->command(-label =>'~Open ', -command=>&menu_file('o'), -accelerator=>'Ctrl+O');
$file->command(-label =>'~Save ', -command=>&menu_file('s'), -accelerator=>'Ctrl+S');
$file->separator();
$file->command(-label =>'~Quit ', -command=>sub{exit}, -accelerator=>'Ctrl+Q');
# Help Menu
$help->command(-label => 'Version');
$help->separator;
$help->command(-label => 'About');
# Menu Bar Accelerators
$mw->bind('<Control-n>', &menu_file('n'));
$mw->bind('<Control-o>', &menu_file('o'));
$mw->bind('<Control-s>', &menu_file('s'));
$mw->bind('<Control-q>', sub{exit});
MainLoop;
sub menu_file {
my $opt=shift;
my $filetypes = [
['Codac files', '.k'],
['All Files', '*' ],
];
if($opt eq 's'){
my $txt_ent_script = $mw->getSaveFile(-filetypes=>$filetypes, -initialfile=>'jitter', -defaultextension=>'.k');
print "Output filename: $txt_ent_script\n";
}
}

Answer 1

That's because &menu_file('n') is syntax for invoking a subroutine (more details). Instead, you have to do it like this:
$mw->bind('<Control-n>' => sub{menu_file('n')});
Or like this:
$mw->bind('<Control-n>' => [\&menu_file, 'n']);