C_IFSWS
if (Xlength(cs, cp) == 0 && ctype(c, C_IFSWS))
&& ctype(cp[-1], C_IFSWS))
|| (!ctype(c, C_IFSWS) && (c || word == IFS_NWS)))
word = ctype(c, C_IFSWS) ? IFS_WS : IFS_NWS;
while (*p && ctype(*p, C_IFS) && ctype(*p, C_IFSWS))
setctypes(" \t\n", C_IFSWS);