Here is my suggestion:

foreach $line (@arr) {
      if ( $line =~ m{\s+\d+:\s+\d+\s*:(\S+:\S+:D\n?)$}g ) {
        #do something
  }
}
[download]

To clarify: Are you concerned of matching (0:0:D) i.e. as per your statement "which I am scanning for processes which have a ':D' appended to the back of the :0:0"? The current expression given by you matches

13: 5456  :0:0   14: 5444  :0:0   15: 5445  :0:0   16: 14682 :1:0:D
17: 5450  :0:0   19: 5453  :0:0   20: 14626 :0:0:D
[download]