Tcl, 515
set d [read stdin]
if {![regexp {^[hq9\+HQ]*$} $d]} {puts "Source code contains invalid characters"}
lmap c [split $d {}] {set b { bottles of beer}
switch -- $c H {puts "Hello, world"} Q {puts $d} 9 {for {set i 99} {$i>3} {incr i -1} {puts "$i$b on the wall,
$i$b.
Take one down, pass it around,
[expr $i-1]$b on the wall.
"}
puts "2$b on the wall,
2$b.
Take one down, pass it around,
1 bottle of beer on the wall.
1 bottle of beer on the wall,
1 bottle of beer.
Take one down, pass it around,
No$b on the wall."}}
Just a bit golfed, still smaller than C and the correct 99 Bottles of beer end verse.