[dsevil]

Original author writes: >>> "Quick aside: I first learned about these ASCII delimiters while working with .fec files. For whatever reason, the Federal Election Commission in the United States also decided that they needed to ditch the comma, but they landed on using ASCII character 28 which is supposed to be used as a file separator not a field saparator. I have no idea why they picked that one when 31 was right there. Anyway, the FEC also has a tool called fs2comma.exe that turns it back into a CSV format, and a couple of years I filed a FOIA request and got the source code."

I can only speculate on this but in Perl, for fake multimensional arrays à la `$foo{$x,$y,$z}`[^1], Perl uses ASCII character 28 (U+001C INFORMATION SEPARATOR FOUR) as its default subscript separator. Perl borrowed this feature from AWK, which uses the same character by default for the same purpose.

Based on Perl, I initally used that same character for that same purpose in a project or two. I cannot speculate on why Aho, Weinberger, and/or Kernighan chose that character. (On or before 1977.)

[^1]: Not to be confused with nested array (or hash) references in Perl, a truer form of multimensional arrays: `$foo->[$x]->{$y}->[$z]`