diff --git a/server/src/tools/checks.py b/server/src/tools/checks.py
index dfeaae6..f158718 100644
--- a/server/src/tools/checks.py
+++ b/server/src/tools/checks.py
@@ -120,6 +120,15 @@ class UndeclaredVariableCheck(Visitor):
                         base = text.split("(", 1)[0]  # Handle array syntax
                         if not base.startswith("::"):
                             locals_set.add(base)
+                elif name == "regsub" and node.args:
+                    # regsub ?switches? exp string subSpec ?varName?
+                    # If a varName is provided as the last arg, treat it as a local
+                    last_arg = node.args[-1]
+                    text = _word_text(last_arg)
+                    if text:
+                        base = text.split("(", 1)[0]
+                        if base and not base.startswith("::"):
+                            locals_set.add(base)
                 elif name == "foreach" and len(node.args) >= 3:
                     # foreach varlist1 list1 ?varlist2 list2 ...? body
                     # Treat loop variables as locals within the proc