Characters that killed a render, what may sit next to a klammer, and ref/

A character written in the ^...^ mnemonic form -- ^oe^, ^zz^, ^hello^ --
used to kill ktext outright: no message, no output, and an exit status
that looked like a crash because it was one.  Only the forms that happen
to spell hexadecimal digits escaped, and they were right by luck rather
than by reading.  Any caret form that names no character is now a located
error that quotes what was written.

A klammer may now sit inside square brackets and braces as it already
could inside parentheses, and may be followed by the punctuation that
ends a sentence: [@i word@], {@b word@}, @i word@'s.  The rule is a fixed
list of characters, because none of them can occur inside a klammer name
and so none of them is ambiguous next to a delimiter.  A letter still
cannot: "x@" is the named closing delimiter, so a letter before "@" has
two readings and no rule can separate them.

The abbreviations an author writes -- the hyphen form @i-word, a klammer
glued to its neighbouring punctuation -- are now recognised as author
conveniences only.  They are not applied to @@ definitions or @@@ system
commands, which are written by someone who needs no such shorthand and
whose forms are already whole.

Also fixed, each of them silent: an exported shell function in the
environment broke every @eval in the document; a line break written with
@nl was destroyed when it passed through a klammer that generates a
table, printing as \textbackslash{}newline in the finished PDF; and
"kdesc --coverage" shortened its file column by comparing the spelling of
a path rather than the path, so a klammer set reached by a symbolic link
showed a full path where its neighbours showed a short one.

New in the distribution: ref/, a small klammerset that describes the
Klammermachine's own tables in Klammertext.  It currently provides the
character tables -- the diacritics and the extended Latin letters -- as
klammers that render to any target, so the documentation of what can be
written cannot drift from what the machine accepts.  It is early, and
will grow.

The Klammertext taxonomy now has a section on targets, describes the
@@@klammerset system command alongside the other three, and states the
precedence of "^" -- what a caret means before a letter, a digit, a
punctuation character, and a quote, in one ordered list.

(from dev 6594c7ff8c1f)

mac/state.cpp

@@ -1,3 +1,5 @@
+#include <algorithm>
+#include <cctype>
 #include <regex>
 #include <iostream>
 #include <map>
@@ -149,11 +151,38 @@ void State::replace(const std::string& name, const std::string& value, bool erro
     set(name, value, true);
 }
 
+// Whether a name can be used as a state variable at all.  POSIX allows only
+// [A-Za-z_][A-Za-z0-9_]* in an environment variable name, and the katomizer's
+// karg pattern (\*\w+\*) accepts no more, so a name outside this set could
+// never be written as *NAME* in the first place.
+//
+// The one that matters in practice: bash EXPORTS SHELL FUNCTIONS, and they
+// arrive in environ as "BASH_FUNC_name%%=() { ... }".  Those were being taken
+// as state variables and then emitted into the @eval Python globals as
+// assignments, where "BASH_FUNC_mdpdf%%" is not a valid identifier -- so a
+// single "export -f" anywhere in a user's shell profile made EVERY @eval fail
+// with a Python SyntaxError, reported against whichever .k file happened to
+// hold the first one (sks/date/date.k).  Nothing in the message named the
+// environment.  Found 2026-09-04 by the dual-compiler confidence run.
+static bool usable_variable_name(const std::string& name)
+{
+    if (name.empty())
+        return false;
+    if (!std::isalpha(static_cast<unsigned char>(name[0])) && name[0] != '_')
+        return false;
+    return std::all_of(name.begin(), name.end(), [](unsigned char c) {
+        return std::isalnum(c) != 0 || c == '_'; });
+}
+
 void State::add_environment_frame()
 {
     open_frame(klammerstate::shell_environment_name);
     for (const auto& [name, value] : environment_variables()) {
-        set(name, value);
+        // Silently skipped rather than reported: the user can read it off
+        // their own shell profile, it changes no output, and an exported
+        // function would otherwise warn on every run.
+        if (usable_variable_name(name))
+            set(name, value);
     }
 }