Execute HQ9+/Tcl
Execute HQ9+/Tcl is part of RCHQ9+. You may find other members of RCHQ9+ at Category:RCHQ9+.
Execute HQ9+/Tcl is an implementation of HQ9+.
Other implementations of HQ9+.
These implementations have the feature that they are quines of themselves in the language that they accept (so long as you take a generous definition of what to ignore; the HQ9+ definition is ambiguous enough that it allows such an interpretation). So the implementation of a language with a quine operation is a quine in the language implemented. This feels like a rather appropriate restriction...
Interpreter
set d [read [expr {$argc?[open [lindex $argv 0]]:"stdin"}]]
for {set i [set a 0]} {$i<[string len $d]} {incr i} {
switc\u0068 -- [string index [string tolower $d] $i] \u0068 {
puts "\u0048ello, world!"
} q {puts -nonewline $d} [expr 10-1] {
for {set b [expr 100-1]} 1 {} {
puts "$b bottle[expr {$b-1?{s}:{}}] of beer on t\u0068e wall"
puts "$b bottle[expr {$b-1?{s}:{}}] of beer"
incr b -1
puts "take one down and pass it around"
puts "$b bottle[expr {$b-1?{s}:{}}] of beer on t\u0068e wall"
if {$b} {puts ""} else break
}
} \x2b {incr a}
}
Compiler
To be fair, this compiler then immediately executes the code. Replace the eval with puts to see what it generates.
set d [read [expr {[set a $argc]?[open [lindex $argv [set a 0]]]:"stdin"}]]
eval [string map [list \u0068 {puts "\u0048ello, world!";} q \
[list puts -nonewline $d]\n \071 {for {set b [expr 100-1]} 1 {} {
puts "$b bottle[expr {$b-1?{s}:{}}] of beer on t\u0068e wall"
puts "$b bottle[expr {$b-1?{s}:{}}] of beer"
incr b -1
puts "take one down and pass it around"
puts "$b bottle[expr {$b-1?{s}:{}}] of beer on t\u0068e wall"
if {$b} {puts ""} else break
};} \x2b {incr a;}
] [regsub -all {[\u0000-*,-8:-gi-pr-\uffff]*} $d {}]]