macro_rules! bigprint {
    ( __end $line1:expr, $line2:expr, $line3:expr, $line4:expr, $line5:expr ) => {
        compile_error!(concat!("\n", $line1, "\n", $line2, "\n", $line3, "\n", $line4, "\n", $line5));
    };
    ( __cont (d $( $letters:tt )*) | $line1:expr, $line2:expr, $line3:expr, $line4:expr, $line5:expr ) => {
        bigprint!( __cont ($($letters)*) | concat!($line1, " OOOO  "), concat!($line2, " O   O "), concat!($line3, " O   O "), concat!($line4, " O   O "), concat!($line5, " OOOO  "));
    };
    ( __cont (e $( $letters:tt )*) | $line1:expr, $line2:expr, $line3:expr, $line4:expr, $line5:expr ) => {
        bigprint!( __cont ($($letters)*) | concat!($line1, " OOOOO "), concat!($line2, " O     "), concat!($line3, " OOO   "), concat!($line4, " O     "), concat!($line5, " OOOOO "));
    };
    ( __cont (h $( $letters:tt )*) | $line1:expr, $line2:expr, $line3:expr, $line4:expr, $line5:expr ) => {
        bigprint!( __cont ($($letters)*) | concat!($line1, " O   O "), concat!($line2, " O   O "), concat!($line3, " OOOOO "), concat!($line4, " O   O "), concat!($line5, " O   O "));
    };
    ( __cont (l $( $letters:tt )*) | $line1:expr, $line2:expr, $line3:expr, $line4:expr, $line5:expr ) => {
        bigprint!( __cont ($($letters)*) | concat!($line1, " O     "), concat!($line2, " O     "), concat!($line3, " O     "), concat!($line4, " O     "), concat!($line5, " OOOOO "));
    };
    ( __cont (o $( $letters:tt )*) | $line1:expr, $line2:expr, $line3:expr, $line4:expr, $line5:expr ) => {
        bigprint!( __cont ($($letters)*) | concat!($line1, "  OOO  "), concat!($line2, " O   O "), concat!($line3, " O   O "), concat!($line4, " O   O "), concat!($line5, "  OOO  "));
    };
    ( __cont (r $( $letters:tt )*) | $line1:expr, $line2:expr, $line3:expr, $line4:expr, $line5:expr ) => {
        bigprint!( __cont ($($letters)*) | concat!($line1, " OOOO  "), concat!($line2, " O   O "), concat!($line3, " OOOO  "), concat!($line4, " O  O  "), concat!($line5, " O   O "));
    };
    ( __cont (w $( $letters:tt )*) | $line1:expr, $line2:expr, $line3:expr, $line4:expr, $line5:expr ) => {
        bigprint!( __cont ($($letters)*) | concat!($line1, " O   O "), concat!($line2, " O O O "), concat!($line3, " O O O "), concat!($line4, " O O O "), concat!($line5, "  O O  "));
    };
    ( __cont (_ $( $letters:tt )*) | $line1:expr, $line2:expr, $line3:expr, $line4:expr, $line5:expr ) => {
        bigprint!( __cont ($($letters)*) | concat!($line1, "       "), concat!($line2, "       "), concat!($line3, "       "), concat!($line4, "       "), concat!($line5, "       "));
    };
    ( __cont ($foo:tt $( $letters:tt )*) | $line1:expr, $line2:expr, $line3:expr, $line4:expr, $line5:expr ) => {
        compile_error!(concat!("unmatched: ", stringify!($foo)));
    };
    ( __cont ( ) | $line1:expr, $line2:expr, $line3:expr, $line4:expr, $line5:expr ) => {
        bigprint!( __end $line1, $line2, $line3, $line4, $line5);
    };
    ( $( $letters:tt )* ) => {
        bigprint!( __cont ($($letters)*) | "", "", "", "", "");
    };
}

bigprint!(h e l l o _ w o r l d);