use constant NOTICE => 'please be sure that XXX is installed first';

# many lines later

print NOTICE;

##</code><code>##

if ($language eq 'perlmonks_terse') {
    use constant NOTICE => 'do perlfaq XXX, use strict; and use CGI;';
}
elsif ($language eq 'aussie') [
    use constant NOTICE => 'install the bloody XXX first, you dopey drongo';
}
else {
    use constant NOTICE => 'please be sure that XXX is installed first';
}