diff --git a/maven-core/src/main/java/org/apache/maven/plugin/PluginParameterExpressionEvaluator.java b/maven-core/src/main/java/org/apache/maven/plugin/PluginParameterExpressionEvaluator.java
index 47bf555345..a9ed4be3be 100644
--- a/maven-core/src/main/java/org/apache/maven/plugin/PluginParameterExpressionEvaluator.java
+++ b/maven-core/src/main/java/org/apache/maven/plugin/PluginParameterExpressionEvaluator.java
@@ -172,11 +172,11 @@ public class PluginParameterExpressionEvaluator implements TypeAwareExpressionEv
                 int pathSeparator = expression.indexOf('/');
 
                 if (pathSeparator > 0) {
-                    String pathExpression = expression.substring(1, pathSeparator);
+                    String pathExpression = expression.substring(0, pathSeparator);
                     value = ReflectionValueExtractor.evaluate(pathExpression, session);
                     value = value + expression.substring(pathSeparator);
                 } else {
-                    value = ReflectionValueExtractor.evaluate(expression.substring(1), session);
+                    value = ReflectionValueExtractor.evaluate(expression, session);
                 }
             } catch (Exception e) {
                 // TODO don't catch exception
@@ -198,7 +198,7 @@ public class PluginParameterExpressionEvaluator implements TypeAwareExpressionEv
                     value = ReflectionValueExtractor.evaluate(pathExpression, project);
                     value = value + expression.substring(pathSeparator);
                 } else {
-                    value = ReflectionValueExtractor.evaluate(expression.substring(1), project);
+                    value = ReflectionValueExtractor.evaluate(expression, project);
                 }
             } catch (Exception e) {
                 // TODO don't catch exception
@@ -214,11 +214,11 @@ public class PluginParameterExpressionEvaluator implements TypeAwareExpressionEv
                 int pathSeparator = expression.indexOf('/');
 
                 if (pathSeparator > 0) {
-                    String pathExpression = expression.substring(1, pathSeparator);
+                    String pathExpression = expression.substring(0, pathSeparator);
                     value = ReflectionValueExtractor.evaluate(pathExpression, mojoExecution);
                     value = value + expression.substring(pathSeparator);
                 } else {
-                    value = ReflectionValueExtractor.evaluate(expression.substring(1), mojoExecution);
+                    value = ReflectionValueExtractor.evaluate(expression, mojoExecution);
                 }
             } catch (Exception e) {
                 // TODO don't catch exception
@@ -234,11 +234,11 @@ public class PluginParameterExpressionEvaluator implements TypeAwareExpressionEv
                 PluginDescriptor pluginDescriptor = mojoDescriptor.getPluginDescriptor();
 
                 if (pathSeparator > 0) {
-                    String pathExpression = expression.substring(1, pathSeparator);
+                    String pathExpression = expression.substring(0, pathSeparator);
                     value = ReflectionValueExtractor.evaluate(pathExpression, pluginDescriptor);
                     value = value + expression.substring(pathSeparator);
                 } else {
-                    value = ReflectionValueExtractor.evaluate(expression.substring(1), pluginDescriptor);
+                    value = ReflectionValueExtractor.evaluate(expression, pluginDescriptor);
                 }
             } catch (Exception e) {
                 throw new ExpressionEvaluationException(
@@ -251,11 +251,11 @@ public class PluginParameterExpressionEvaluator implements TypeAwareExpressionEv
                 int pathSeparator = expression.indexOf('/');
 
                 if (pathSeparator > 0) {
-                    String pathExpression = expression.substring(1, pathSeparator);
+                    String pathExpression = expression.substring(0, pathSeparator);
                     value = ReflectionValueExtractor.evaluate(pathExpression, session.getSettings());
                     value = value + expression.substring(pathSeparator);
                 } else {
-                    value = ReflectionValueExtractor.evaluate(expression.substring(1), session.getSettings());
+                    value = ReflectionValueExtractor.evaluate(expression, session.getSettings());
                 }
             } catch (Exception e) {
                 // TODO don't catch exception
diff --git a/maven-core/src/main/java/org/apache/maven/plugin/PluginParameterExpressionEvaluatorV4.java b/maven-core/src/main/java/org/apache/maven/plugin/PluginParameterExpressionEvaluatorV4.java
index 56532bc051..2357af54ef 100644
--- a/maven-core/src/main/java/org/apache/maven/plugin/PluginParameterExpressionEvaluatorV4.java
+++ b/maven-core/src/main/java/org/apache/maven/plugin/PluginParameterExpressionEvaluatorV4.java
@@ -175,11 +175,11 @@ public class PluginParameterExpressionEvaluatorV4 implements TypeAwareExpression
                 int pathSeparator = expression.indexOf('/');
 
                 if (pathSeparator > 0) {
-                    String pathExpression = expression.substring(1, pathSeparator);
+                    String pathExpression = expression.substring(0, pathSeparator);
                     value = ReflectionValueExtractor.evaluate(pathExpression, session);
                     value = value + expression.substring(pathSeparator);
                 } else {
-                    value = ReflectionValueExtractor.evaluate(expression.substring(1), session);
+                    value = ReflectionValueExtractor.evaluate(expression, session);
                 }
             } catch (Exception e) {
                 // TODO don't catch exception
@@ -206,7 +206,7 @@ public class PluginParameterExpressionEvaluatorV4 implements TypeAwareExpression
                     value = ReflectionValueExtractor.evaluate(pathExpression, project);
                     value = value + expression.substring(pathSeparator);
                 } else {
-                    value = ReflectionValueExtractor.evaluate(expression.substring(1), project);
+                    value = ReflectionValueExtractor.evaluate(expression, project);
                 }
             } catch (Exception e) {
                 // TODO don't catch exception
@@ -223,11 +223,11 @@ public class PluginParameterExpressionEvaluatorV4 implements TypeAwareExpression
                 int pathSeparator = expression.indexOf('/');
 
                 if (pathSeparator > 0) {
-                    String pathExpression = expression.substring(1, pathSeparator);
+                    String pathExpression = expression.substring(0, pathSeparator);
                     value = ReflectionValueExtractor.evaluate(pathExpression, mojoExecution);
                     value = value + expression.substring(pathSeparator);
                 } else {
-                    value = ReflectionValueExtractor.evaluate(expression.substring(1), mojoExecution);
+                    value = ReflectionValueExtractor.evaluate(expression, mojoExecution);
                 }
             } catch (Exception e) {
                 // TODO don't catch exception
@@ -246,11 +246,11 @@ public class PluginParameterExpressionEvaluatorV4 implements TypeAwareExpression
                         mojoExecution.getMojoDescriptor().getPluginDescriptor();
 
                 if (pathSeparator > 0) {
-                    String pathExpression = expression.substring(1, pathSeparator);
+                    String pathExpression = expression.substring(0, pathSeparator);
                     value = ReflectionValueExtractor.evaluate(pathExpression, pluginDescriptor);
                     value = value + expression.substring(pathSeparator);
                 } else {
-                    value = ReflectionValueExtractor.evaluate(expression.substring(1), pluginDescriptor);
+                    value = ReflectionValueExtractor.evaluate(expression, pluginDescriptor);
                 }
             } catch (Exception e) {
                 throw new ExpressionEvaluationException(
@@ -263,11 +263,11 @@ public class PluginParameterExpressionEvaluatorV4 implements TypeAwareExpression
                 int pathSeparator = expression.indexOf('/');
 
                 if (pathSeparator > 0) {
-                    String pathExpression = expression.substring(1, pathSeparator);
+                    String pathExpression = expression.substring(0, pathSeparator);
                     value = ReflectionValueExtractor.evaluate(pathExpression, session.getSettings());
                     value = value + expression.substring(pathSeparator);
                 } else {
-                    value = ReflectionValueExtractor.evaluate(expression.substring(1), session.getSettings());
+                    value = ReflectionValueExtractor.evaluate(expression, session.getSettings());
                 }
             } catch (Exception e) {
                 // TODO don't catch exception
diff --git a/maven-core/src/main/java/org/apache/maven/plugin/ReflectionValueExtractor.java b/maven-core/src/main/java/org/apache/maven/plugin/ReflectionValueExtractor.java
index 6590ca6099..64d5453661 100644
--- a/maven-core/src/main/java/org/apache/maven/plugin/ReflectionValueExtractor.java
+++ b/maven-core/src/main/java/org/apache/maven/plugin/ReflectionValueExtractor.java
@@ -18,6 +18,8 @@
  */
 package org.apache.maven.plugin;
 
+import java.lang.ref.Reference;
+import java.lang.ref.WeakReference;
 import java.lang.reflect.Array;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
@@ -41,7 +43,7 @@ class ReflectionValueExtractor {
      * This approach prevents permgen space overflows due to retention of discarded
      * classloaders.
      */
-    private static final Map<Class<?>, ClassMap> CLASS_MAPS = new WeakHashMap<>();
+    private static final Map<Class<?>, WeakReference<ClassMap>> CLASS_MAPS = new WeakHashMap<>();
 
     static final int EOF = -1;
 
@@ -285,12 +287,13 @@ class ReflectionValueExtractor {
     }
 
     private static ClassMap getClassMap(Class<?> clazz) {
-        ClassMap classMap = CLASS_MAPS.get(clazz);
+        Reference<ClassMap> ref = CLASS_MAPS.get(clazz);
+        ClassMap classMap = ref != null ? ref.get() : null;
 
         if (classMap == null) {
             classMap = new ClassMap(clazz);
 
-            CLASS_MAPS.put(clazz, classMap);
+            CLASS_MAPS.put(clazz, new WeakReference<>(classMap));
         }
 
         return classMap;