Only clear to those with a heavy UNIX background-- I understood and correctly interpreted it on first read, but the concept of a "regular file" is a bit in the wonk territory for most users, though the implication on symbolic links is a very practical one that surely lead to the removal (in the implementations where it was removed) of this option, since its very surprising that copying a directory heirarchy would cause symbolic links to become copies of what they linked to, instead of remaining symbolic links in the resulting directory.
My first thought was 'regular expression'. I've also never heard of the classification of a 'special' file in *nix land either (at least as utility flags go).
The snippet of code makes it very clear what the difference is, no?
flag_copy_as_regular = 1 VS flag_copy_as_regular = 0, where regular would be a "regular" and not "special" file.