use constant = {
...
}

sub routine {
    my $mouse_mode = set_mouse_mode;
    ...
    ...
    END {
        if ( $mouse_mode ) {
            print UNSET_EXT_MODE_MOUSE_1005     if $mouse_mode == 3;
            print UNSET_SGR_EXT_MODE_MOUSE_1006 if $mouse_mode == 4;
            print UNSET_ANY_EVENT_MOUSE_1003;
        }
    }
}