I didn't mean for "not reasonable" to sound like your request is unreasonable. Just that setting the warning there isn't ideal because my_sub could be something like:

sub my_sub {
    my $closed_handle = shift;
    die "For some reason our handle isn't closed yet."
        if $closed_handle->opened;
}
[download]

...or

close $fh or my_sub($fh);

sub my_sub {
    my $handle = shift;
    my $error = $handle->error;
    die "Got this error code: $error\n" if $error;
}
[download]

...or even...

# Open a handle only if it's not opened.
sub my_sub {
    open $_[0], '<', $_[1] if !$_[0]->opened;
}
[download]