If anyone tells you that a string (like a command-line argument) contains a list of smaller strings with a specific separator character in between them, immediately ask "In that case, what happens if the separator character needs to appear in one of the list items?" Instant knee-jerk reflex.

There's more than one good answer. Like "you can escape the separator with this other character" (in which case you know what question #2 is). Or "here is a specific reason why it _can't possibly_ be necessary to put the separator in a list item" (maybe list items are something like numbers or C identifiers which already have a restricted character set).

But if they just say it doesn't seem _likely_, or worse still, demand you justify why you need to, run a mile from whatever software is under discussion.