tar
tar
[Megan and White Hat stand next to a nuclear bomb. The bomb has a hatch open on top, and a small blinking screen. The two people are shouting off-screen.] Megan: Rob! You use Unix! White Hat: Come quick!
[Megan, White Hat, and Rob look at the screen on the bomb. Rob peers closely. The screen is on the bomb, but is shown at the top of the panel in black with white letters, except "tar" and the last underscore which is in gray and "ten" which is black but written in a white box. The text reads:]
[They all stand in the same position, but without the text displayed. Beat panel.]
[Still in the same position but White Hat becomes impatient.] White Hat: ...Rob? Rob: I'm so sorry.

tar ("tape archive") is a Unix application that creates (and extracts) archives in the ".tar" format. It is typically used through the text-based terminal, using cryptic single-letter arguments such as " tar -cvf archive.tar * ". The comic alludes to the fact that despite years of use of the command, it's still hard to remember the arguments without searching for them, such as with Google.
The joke here is that a "tar" command with perfect syntax on the first try without outside help is such a daunting task that even Rob can't overcome it with confidence, and apologizes for not being able to prevent their imminent death.
The fact that Megan and White Hat assume that Rob can disarm the nuclear bomb because he uses Unix can be referring to an over-generalization fallacy that a partaker in a practice is an expert of a practice. Not all people who use Unix necessarily know how to use tar commands. Then again, since he's the only person nearby who knows any Unix and thus their only hope, their fallacy is pretty justified.
The title text points out that while much of computing changes very quickly, the tar program, which is very old (originating ca. 1975), is still around and heavily used. And yet, Randall complains he still cannot type out a line of tar command with correct flags without having to look the flags up. Tar is a very common command that Unix users will come across regularly, much like Windows users will come across .zip files. Depending on the flavor of Unix, the order of the flags, or the lack or inclusion of a '-' could render the command incorrect. Most true Unixes (AIX, HPUX, Solaris) not using the GNU utilities would give an error on the above tar example. For such a simple command, it is one that most people need to look up references to use.
There is probably also a pun on " tarbomb ," a poorly created tar archive that, when extracted, dumps a load of files into the current directory that the user has to clean up. And although the bomb looks more like Fat Man , the type of bomb that was used over Nagasaki , at least size-wise, it may also be a pun on the name of the largest ever hydrogen bomb which was called the Tsar Bomba (translation: "emperor bomb").
In 208: Regular Expressions Cueball saves the day by knowing regular expressions , although in the title text it is alluded to how easy these may also miss a character.
Rob may refer to Rob Pike , who was a member of the team at AT&T who created Unix.
[Megan and White Hat stand next to a nuclear bomb. The bomb has a hatch open on top, and a small blinking screen. The two people are shouting off-screen.] Megan: Rob! You use Unix! White Hat: Come quick!
[Megan, White Hat, and Rob look at the screen on the bomb. Rob peers closely. The screen is on the bomb, but is shown at the top of the panel in black with white letters, except "tar" and the last underscore which is in gray and "ten" which is black but written in a white box. The text reads:]
[They all stand in the same position, but without the text displayed. Beat panel.]
[Still in the same position but White Hat becomes impatient.] White Hat: ...Rob? Rob: I'm so sorry.
