diff --git a/src/Env.php b/src/Env.php
index 8ba4d0e..c8b9416 100644
--- a/src/Env.php
+++ b/src/Env.php
@@ -20,10 +20,4 @@ class Env extends Hash
 
         throw new MadLispException("symbol $key not defined in env");
     }
-
-    public function set(string $key, $value)
-    {
-        $this->data[$key] = $value;
-        return $value;
-    }
 }
diff --git a/src/Hash.php b/src/Hash.php
index 0b4bcc0..ce09a70 100644
--- a/src/Hash.php
+++ b/src/Hash.php
@@ -11,4 +11,10 @@ class Hash extends Collection
 
         throw new MadLispException("hash does not contain key $key");
     }
+
+    public function set(string $key, $value)
+    {
+        $this->data[$key] = $value;
+        return $value;
+    }
 }
diff --git a/src/Lib/Collections.php b/src/Lib/Collections.php
index fdeda31..1f1d105 100644
--- a/src/Lib/Collections.php
+++ b/src/Lib/Collections.php
@@ -30,12 +30,16 @@ class Collections implements ILib
             fn (...$args) => new Vector($args)
         ));
 
-        // Other
+        // Read information
 
         $env->set('empty?', new CoreFunc('empty?', 'Return true if collection is empty.', 1, 1,
             fn (Collection $a) => $a->count() == 0
         ));
 
+        $env->set('get', new CoreFunc('get', 'Get the item from first argument (collection) by using the second argument as index or key.', 2, 2,
+            fn (Collection $a, $b) => $a->get($b)
+        ));
+
         $env->set('len', new CoreFunc('len', 'Return the length of string or number of elements in collection.', 1, 1,
             function ($a) {
                 if ($a instanceof Collection) {
@@ -48,6 +52,8 @@ class Collections implements ILib
             }
         ));
 
+        // Get partial list
+
         $env->set('first', new CoreFunc('first', 'Return the first element of a sequence or null.', 1, 1,
             fn (Seq $a) => $a->getData()[0] ?? null
         ));
@@ -74,6 +80,18 @@ class Collections implements ILib
             }
         ));
 
+        // Manipulate list
+
+        $env->set('push', new CoreFunc('push', 'Push the remaining arguments at the end of the sequence (first argument).', 2, -1,
+            function (Seq $a, ...$b) {
+                $data = $a->getData();
+                foreach ($b as $c) {
+                    $data[] = $c;
+                }
+                return $a::new($data);
+            }
+        ));
+
         $env->set('map', new CoreFunc('map', 'Apply the first argument (function) to all elements of second argument (sequence).', 2, 2,
             function (Func $f, Seq $a) {
                 return $a::new(array_map($f->getClosure(), $a->getData()));
@@ -86,6 +104,28 @@ class Collections implements ILib
             }
         ));
 
+        // Hash map functions
+
+        $env->set('key?', new CoreFunc('key?', 'Return true if first argument (hash-map) contains the second argument as key.', 2, 2,
+            fn (Hash $a, string $b) => $a->has($b)
+        ));
+
+        $env->set('set', new CoreFunc('set', 'Create new hash-map from first argument and set key (second argument) to value given by third argument.', 3, 3,
+            function (Hash $a, string $key, $val) {
+                // Immutable version
+                $hash = new Hash($a->getData());
+                $hash->set($key, $val);
+                return $hash;
+            }
+        ));
+
+        $env->set('set!', new CoreFunc('set!', 'Modify the hash-map (first argument) and set key (second argument) to value given by third argument and return the value.', 3, 3,
+            function (Hash $a, string $key, $val) {
+                // Mutable version
+                return $a->set($key, $val);
+            }
+        ));
+
         $env->set('keys', new CoreFunc('keys', 'Return the keys of a hash-map as a list.', 1, 1,
             fn (Hash $a) => new MList(array_keys($a->getData()))
         ));