diff --git a/man/remind.1.in b/man/remind.1.in
index 46e5c111..aa671bf2 100644
--- a/man/remind.1.in
+++ b/man/remind.1.in
@@ -3649,6 +3649,14 @@ As an example, the following two expressions are equivalent:
 .fi
 .RE
 .TP
+.B isconst(x_any)
+Evaluates its argument and then \fIthrows away\fR the value, returning
+1 if the expression is constant or 0 if it is non-constant.  Note that
+\fBisconst\fR does not take into account the context; if \fIarg\fR is
+a constant expression but evaluated in a non-constant context,
+\fBisconst\fR will still return 1.  For details about constant vs.
+non-constant expressions, see the section "NON-CONSTANT EXPRESSIONS"
+.TP
 .B isdst([d_date [,t_time]]) \fRor\fB isdst(q_datetime)
 Returns a positive number if daylight saving time is in
 effect on the specified date and time.  \fIDate\fR
@@ -3951,6 +3959,11 @@ The second REM statement sets up the 14-day blue-box cycle with a similar
 adjustment made by AFTER in conjunction with _garbhol.
 .RE
 .TP
+.B nonconst(x_arg)
+Returns the argument \fIarg\fR unchanged, but forces the expression
+to be considered \fInon-constant\fR.  For details, see the section
+"NON-CONSTANT EXPRESSIONS"
+.TP
 .B now()
 Returns the current system time, as a \fBTIME\fR type.  This may be
 the actual time, or a time supplied on the command line.
@@ -5691,7 +5704,9 @@ to consider it non-constant:
 .RS
 .TP
 .B o
-A global variable
+A global variable that has been assigned the result of a non-constant
+expression, or that has been assigned a value in a \fInon-constant
+context\fR (to be described later.)
 .TP
 .B o
 A system variable
@@ -5713,19 +5728,36 @@ The use of an OMITFUNC
 The use of a relative SCANFROM
 .RE
 .PP
-Note that \fBRemind\fR checks expressions for non-constantness
-\fIin isolation\fR.  It does not trace data flow.  For example.
-a human can easily see that the expression in the REM command
-below is actually constant, but \fBRemind\fR does not look
-at the preceding assignment.  It simply looks at the expression \fBd\fR
-in isolation and considers that the global variable \fBd\fR
-might not be constant.
+Whenever a variable is assigned a value, \fBRemind\fR tracks whether
+or not the expression whose value it was assigned is constant or
+non-constant.  Additionally, variables that are assigned in a
+non-constant context are always assumed to be non-constant.
+A non-constant context is the code in the scope of an \fBIF\fR
+statement where the \fBIF\fR expression is non-constant.
+.PP
+Here are some examples that should make things clear:
 .PP
 .nf
-        SET d '2025-06-01'
-        REM [d] MSG Hello!
+        SET d '2025-06-01'        # d is constant
+        REM [d] MSG Hello!        # eligible for purging
+
+        SET d today() - 3         # d is non-constant
+        REM [d] MSG Hello!        # not eligible for purging
+
+        IF wkdaynum(today()) == 3
+            set d '2025-06-01'    # d is non-constant
+        ELSE
+            set d '2026-01-01'    # d is non-constant
+        ENDIF
 .fi
 .PP
+Note that within the \fBIF\fR...\fBENDIF\fR scope, any assignments
+are non-constant because the code flow depends on today's date, which
+could change in subsequent \fBRemind\fR runs.
+.PP
+Variables initialized on the command-line with the \fB\-i\fR flag are
+\fIalways\fR considered to be non-constant.
+.PP
 The \fBn\fR debugging flag prints a message to standard error whenever
 \fBRemind\fR decides that an expression is non-constant.  This can produce
 a large amount of output, so if you want to find out why \fBRemind\fR considers
diff --git a/src/dorem.c b/src/dorem.c
index bb49908c..d94b4379 100644
--- a/src/dorem.c
+++ b/src/dorem.c
@@ -649,7 +649,7 @@ int ParseRem(ParsePtr s, Trigger *trig, TimeTrig *tim)
             strtolower(trig->omitfunc);
             /* An OMITFUNC counts as a nonconst_expr! */
             s->expr_happened = 1;
-            nonconst_debug(s->nonconst_expr, "OMITFUNC counts as a non-constant expression");
+            nonconst_debug(s->nonconst_expr, tr("OMITFUNC counts as a non-constant expression"));
             s->nonconst_expr = 1;
             DBufFree(&buf);
             break;
@@ -1071,7 +1071,7 @@ static int ParseScanFrom(ParsePtr s, Trigger *t, int type)
             FromDSE(DSEToday - tok.val, &y, &m, &d);
             /* Don't purge reminders with a relative scanfrom */
             s->expr_happened = 1;
-            nonconst_debug(s->nonconst_expr, "Relative SCANFROM counts as a non-constant expression");
+            nonconst_debug(s->nonconst_expr, tr("Relative SCANFROM counts as a non-constant expression"));
             s->nonconst_expr = 1;
             break;
 
diff --git a/src/expr.c b/src/expr.c
index 27fb6232..b76a9ee8 100644
--- a/src/expr.c
+++ b/src/expr.c
@@ -426,7 +426,7 @@ get_var(expr_node *node, Value *ans, int *nonconst)
         return E_NOSUCH_VAR;
     }
     if (v->nonconstant) {
-        nonconst_debug(*nonconst, "Global variable `%s' makes expression non-constant", str);
+        nonconst_debug(*nonconst, tr("Global variable `%s' makes expression non-constant"), str);
         *nonconst = 1;
     }
     return CopyValue(ans, &(v->v));
@@ -883,7 +883,7 @@ evaluate_expr_node(expr_node *node, Value *locals, Value *ans, int *nonconst)
 
     case N_SHORT_SYSVAR:
         /* System var?  Return it and note non-constant expression */
-        nonconst_debug(*nonconst, "System variable `$%s' makes expression non-constant", node->u.name);
+        nonconst_debug(*nonconst, tr("System variable `$%s' makes expression non-constant"), node->u.name);
         *nonconst = 1;
         r = get_sysvar(node, ans);
         DBG(debug_evaluation(ans, r, "$%s", node->u.name));
@@ -891,7 +891,7 @@ evaluate_expr_node(expr_node *node, Value *locals, Value *ans, int *nonconst)
 
     case N_SYSVAR:
         /* System var?  Return it and note non-constant expression */
-        nonconst_debug(*nonconst, "System variable `$%s' makes expression non-constant", node->u.value.v.str);
+        nonconst_debug(*nonconst, tr("System variable `$%s' makes expression non-constant"), node->u.value.v.str);
         *nonconst = 1;
         r = get_sysvar(node, ans);
         DBG(debug_evaluation(ans, r, "$%s", node->u.value.v.str));
@@ -900,7 +900,7 @@ evaluate_expr_node(expr_node *node, Value *locals, Value *ans, int *nonconst)
     case N_BUILTIN_FUNC:
         /* Built-in function?  Evaluate and note non-constant where applicable */
         if (!node->u.builtin_func->is_constant) {
-            nonconst_debug(*nonconst, "Non-constant builtin function `%s' makes expression non-constant", node->u.builtin_func->name);
+            nonconst_debug(*nonconst, tr("Non-constant builtin function `%s' makes expression non-constant"), node->u.builtin_func->name);
             *nonconst = 1;
         }
         return eval_builtin(node, locals, ans, nonconst);
diff --git a/src/var.c b/src/var.c
index 2c9e550a..46329083 100644
--- a/src/var.c
+++ b/src/var.c
@@ -646,6 +646,11 @@ int DoSet (Parser *p)
         } else {
             r = SetVar(DBufValue(&buf), &v, 0);
         }
+        if (DebugFlag & DB_NONCONST) {
+            if (!in_constant_context() && !p->nonconst_expr) {
+                Wprint(tr("Variable assignment considered non-constant because of context"));
+            }
+        }
     }
     if (buf.len > VAR_NAME_LEN) {
         Wprint(tr("Warning: Variable name `%.*s...' truncated to `%.*s'"),
diff --git a/tests/test.cmp b/tests/test.cmp
index 479774ab..f37fa3ec 100644
--- a/tests/test.cmp
+++ b/tests/test.cmp
@@ -24808,28 +24808,34 @@ TRANSLATE "Found cached directory listing for `%s'" ""
 TRANSLATE "Function `%s' defined at %s(%s) should take %d argument%s, but actually takes %d" ""
 TRANSLATE "Function `%s' redefined: previously defined at %s(%s)" ""
 TRANSLATE "GetValidHebDate: Bad adarbehave value %d" ""
+TRANSLATE "Global variable `%s' makes expression non-constant" ""
 TRANSLATE "In" ""
 TRANSLATE "Invalid INFO string: Must be of the form \"Header: Value\"" ""
 TRANSLATE "Invalid translation: Both original and translated must have the same printf-style formatting sequences in the same order." ""
 TRANSLATE "Missing REM type; assuming MSG" ""
 TRANSLATE "No Adar A in %d" ""
 TRANSLATE "No substition function `%s' defined" ""
+TRANSLATE "Non-constant builtin function `%s' makes expression non-constant" ""
 TRANSLATE "Not setting $OnceFile: Already processed a reminder with a ONCE clause" ""
 TRANSLATE "OMIT: UNTIL not allowed; did you mean THROUGH?" ""
+TRANSLATE "OMITFUNC counts as a non-constant expression" ""
 TRANSLATE "POP-OMIT-CONTEXT at %s:%d matches PUSH-OMIT-CONTEXT in different file: %s:%d" ""
 TRANSLATE "Reading `%s': Found in cache" ""
 TRANSLATE "Reading `%s': Opening file on disk" ""
 TRANSLATE "Reading `-': Reading stdin" ""
 TRANSLATE "Reading command `%s': Found in cache" ""
+TRANSLATE "Relative SCANFROM counts as a non-constant expression" ""
 TRANSLATE "SATISFY: constant 0 will never be true" ""
 TRANSLATE "SATISFY: constant \"\" will never be true" ""
 TRANSLATE "SATISFY: expression has no reference to trigdate() or $T..." ""
 TRANSLATE "SECURITY: Won't read non-root-owned file or directory when running as root!" ""
 TRANSLATE "SECURITY: Won't read world-writable file or directory!" ""
 TRANSLATE "Scanning directory `%s' for *.rem files" ""
+TRANSLATE "System variable `$%s' makes expression non-constant" ""
 TRANSLATE "Undefined %s function: `%s'" ""
 TRANSLATE "Unmatched PUSH-OMIT-CONTEXT at %s(%d)" ""
 TRANSLATE "Unrecognized command; interpreting as REM" ""
+TRANSLATE "Variable assignment considered non-constant because of context" ""
 TRANSLATE "Warning: Function name `%s...' truncated to `%s'" ""
 TRANSLATE "Warning: OMIT is ignored if you use OMITFUNC" ""
 TRANSLATE "Warning: SCANFROM is ignored in two-argument form of evaltrig()" ""