Variable "$text" will not stay shared at file line 1
####
(W closure) An inner (nested) named subroutine is referencing a
lexical variable defined in an outer named subroutine.
When the inner subroutine is called, it will see the value of
the outer subroutine's variable as it was before and during the *first*
call to the outer subroutine; in this case, after the first call to the
outer subroutine is complete, the inner and outer subroutines will no
longer share a common value for the variable. In other words, the
variable will no longer be shared.
This problem can usually be solved by making the inner subroutine
anonymous, using the sub {} syntax. When inner anonymous subs that
reference variables in outer subroutines are created, they
are automatically rebound to the current values of such variables.
##
##
sub do_top {
if ( !Exists($tl) ) {
$tl = $mw->Toplevel;
$tl->title('Help');
$tl->geometry("1000x700");
my $frame = $tl->Frame()->pack;
my $lab = $tl->Label()->pack;
my $ent = $tl->Entry()->pack;
#### ANONYMOUS SUB , ANONYMOUS CLOSURE,
#### CLOSED OVER LEXICAL $text
#### $text is lexical to if {} block in do_top
my $text = $tl->Scrolled('Text');
my $push_button2 = sub {
$text->insert( 'end', "You pushed button2\n" );
};
$tl->Button( -text => 'Exit', -command => sub { $tl->destroy; } )->pack;
$tl->Button( -text => 'Open File1', -command => $push_button2 )->pack;
$text->pack();
} else {
$tl->deiconify;
$tl->raise;
}
}