Hi, BaseX team. I'm reporting an exception I saw in BaseX 12.4 in a function call where the fn:replace function refers to $1 in the third argument without having any parenthesized expressions in the second argument. The function call has a mistake, but I'm assuming BaseX should respond differently. replace('full stop.','\.','\\$1') Could not execute XQUERY replace('full stop.','\.','\\$1'): Improper use? Potential bug? Your feedback is welcome: Contact: basex-talk@mailman.uni-konstanz.de Version: BaseX 12.4 Java: Eclipse Adoptium, 17.0.17 OS: Windows 11, amd64 Stack Trace: java.lang.IndexOutOfBoundsException: No group 1 at java.base/java.util.regex.Matcher.start(Matcher.java:482) at java.base/java.util.regex.Matcher.appendExpandedReplacement(Matcher.java:1090) at java.base/java.util.regex.Matcher.appendReplacement(Matcher.java:997) at java.base/java.util.regex.Matcher.replaceAll(Matcher.java:1181) at org.basex.query.func.fn.FnReplace.item(FnReplace.java:103) at org.basex.query.func.fn.FnReplace.item(FnReplace.java:22) at org.basex.query.expr.ParseExpr.value(ParseExpr.java:71) at org.basex.query.CompileContext.preEval(CompileContext.java:257) at org.basex.query.func.StandardFunc.optimize(StandardFunc.java:79) at org.basex.query.expr.Arr.compile(Arr.java:49) at org.basex.query.func.StaticFuncs$FuncRef.compile(StaticFuncs.java:358) at org.basex.query.scope.MainModule.compile(MainModule.java:38) at org.basex.query.QueryCompiler.compile(QueryCompiler.java:41) at org.basex.query.QueryContext.compile(QueryContext.java:369) at org.basex.query.QueryContext.lambda$compile$2(QueryContext.java:312) at org.basex.query.QueryContext.run(QueryContext.java:792) at org.basex.query.QueryContext.compile(QueryContext.java:298) at org.basex.query.QueryProcessor.compile(QueryProcessor.java:78) at org.basex.core.cmd.AQuery.init(AQuery.java:203) at org.basex.core.cmd.AQuery.updating(AQuery.java:150) at org.basex.gui.GUI.execute(GUI.java:421) at org.basex.gui.GUI.lambda$execute$5(GUI.java:375) at java.base/java.lang.Thread.run(Thread.java:840) Best regards, Amanda