A filehandle will bet closed when:

1. It is formally closed with close
2. When it goes out of scope which occurs:
   1. If it is localised to a block and you exit said block, provided no closure of course
   2. When the program exits everything goes out of scope.

Examples, no or die $! for clarity not form.

open F, $file;
close F;
# F is closed

{
    open my $fh, $file;
}
# $fh is closed

open F, $file;
exit 0;
# program is gone and F is closed

# closure
{
    my $fh;
    sub append {
        unless ( $fh ) { open $fh, $file }
    }
}
# closure means $fh is not destroyed, $fh remains open until program e
+xit
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