#! /usr/bin/awk -f

/^[ \t]*#\$.*/ {
    match($0,/^[ \t]*/)
    whitespace=substr($0,RSTART,RLENGTH)
    
    match($0,/#\$.*/)
    command=substr($0,RSTART+2,RLENGTH)

    while (command | getline line) print whitespace line
}

!/^[ \t]*#\$.*/ {
    print $0
}