diff --git a/smnp/ast/node/expression.py b/smnp/ast/node/expression.py
index c1c4382..950ccc8 100644
--- a/smnp/ast/node/expression.py
+++ b/smnp/ast/node/expression.py
@@ -25,7 +25,7 @@ class Or(BinaryOperator):
 class Loop(BinaryOperator):
     def __init__(self, pos):
         super().__init__(pos)
-        self.children.append(NoneNode())
+        self.children.extend([NoneNode(), NoneNode()])
 
     @property
     def parameters(self):
@@ -35,13 +35,22 @@ class Loop(BinaryOperator):
     def parameters(self, value):
         self[3] = value
 
+    @property
+    def filter(self):
+        return self[4]
+
+    @filter.setter
+    def filter(self, value):
+        self[4] = value
+
     @classmethod
-    def loop(cls, left, parameters, operator, right):
+    def loop(cls, left, parameters, operator, right, filter):
         node = cls(left.pos)
         node.left = left
         node.parameters = parameters
         node.operator = operator
         node.right = right
+        node.filter = filter
         return node
 
 
@@ -94,11 +103,19 @@ def LoopParser(input):
         name="loop parameters"
     )
 
+    loopFilter = Parser.allOf(
+        Parser.terminal(TokenType.PERCENT),
+        Parser.doAssert(ExpressionWithoutLoopParser, "filter as bool expression"),
+        createNode=lambda percent, expr: expr,
+        name="loop filter"
+    )
+
     return Parser.allOf(
         ExpressionWithoutLoopParser,
         Parser.optional(loopParameters),
         Parser.terminal(TokenType.DASH, createNode=Operator.withValue),
         StatementParser,
+        Parser.optional(loopFilter),
         createNode=Loop.loop,
         name="dash-loop"
     )(input)
diff --git a/smnp/runtime/evaluators/loop.py b/smnp/runtime/evaluators/loop.py
index e9392bd..eafb343 100644
--- a/smnp/runtime/evaluators/loop.py
+++ b/smnp/runtime/evaluators/loop.py
@@ -20,7 +20,7 @@ class LoopEvaluator(Evaluator):
                 Type.BOOL: cls.boolEvaluator,
                 Type.LIST: cls.listEvaluator,
                 Type.MAP: cls.mapEvaluator
-            }[iterator.type](node, environment, iterator, parameters)
+            }[iterator.type](node, environment, iterator, parameters, node.filter)
 
             environment.scopes.pop(-1)
         except KeyError:
@@ -29,7 +29,7 @@ class LoopEvaluator(Evaluator):
         return Type.list(output)
 
     @classmethod
-    def numberEvaluator(cls, node, environment, evaluatedIterator, parameters):
+    def numberEvaluator(cls, node, environment, evaluatedIterator, parameters, filter):
         output = []
 
 
@@ -40,14 +40,28 @@ class LoopEvaluator(Evaluator):
             if len(parameters) > 0:
                 environment.scopes[-1][parameters[0]] = Type.integer(i)
 
-            output.append(evaluate(node.right, environment).value)
+            if cls.doFilter(filter, environment):
+                output.append(evaluate(node.right, environment).value)
 
 
 
         return output
 
     @classmethod
-    def boolEvaluator(cls, node, environment, evaluatedIterator, parameters):
+    def doFilter(cls, filter, environment):
+        if type(filter) is not NoneNode:
+            evaluation = expressionEvaluator(doAssert=True)(filter, environment).value
+            if evaluation.type != Type.BOOL:
+                raise RuntimeException(f"Expected {Type.BOOL.name.lower()} as filter expression, found {evaluation.type.name.lower()}", filter.pos)
+
+            return evaluation.value
+
+        return True
+
+
+
+    @classmethod
+    def boolEvaluator(cls, node, environment, evaluatedIterator, parameters, filter):
         output = []
 
         if len(parameters) > 0:
@@ -55,13 +69,14 @@ class LoopEvaluator(Evaluator):
 
         condition = evaluatedIterator
         while condition.value:
-            output.append(evaluate(node.right, environment).value)
+            if cls.doFilter(filter, environment):
+                output.append(evaluate(node.right, environment).value)
             condition = expressionEvaluator(doAssert=True)(node.left, environment).value
 
         return output
 
     @classmethod
-    def listEvaluator(cls, node, environment, evaluatedIterator, parameters):
+    def listEvaluator(cls, node, environment, evaluatedIterator, parameters, filter):
         output = []
 
         if len(parameters) > 2:
@@ -74,13 +89,14 @@ class LoopEvaluator(Evaluator):
                 environment.scopes[-1][parameters[0]] = Type.integer(i)
                 environment.scopes[-1][parameters[1]] = value
 
-            output.append(evaluate(node.right, environment).value)
+            if cls.doFilter(filter, environment):
+                output.append(evaluate(node.right, environment).value)
 
         return output
 
 
     @classmethod
-    def mapEvaluator(cls, node, environment, evaluatedIterator, parameters):
+    def mapEvaluator(cls, node, environment, evaluatedIterator, parameters, filter):
         output = []
 
         if len(parameters) > 3:
@@ -99,6 +115,7 @@ class LoopEvaluator(Evaluator):
                 environment.scopes[-1][parameters[2]] = value
                 i += 1
 
-            output.append(evaluate(node.right, environment).value)
+            if cls.doFilter(filter, environment):
+                output.append(evaluate(node.right, environment).value)
 
         return output
diff --git a/smnp/token/tokenizer.py b/smnp/token/tokenizer.py
index 7c91ab1..277badb 100644
--- a/smnp/token/tokenizer.py
+++ b/smnp/token/tokenizer.py
@@ -29,6 +29,7 @@ tokenizers = (
     defaultTokenizer(TokenType.CLOSE_ANGLE),
     defaultTokenizer(TokenType.SEMICOLON),
     defaultTokenizer(TokenType.ASTERISK),
+    defaultTokenizer(TokenType.PERCENT),
     defaultTokenizer(TokenType.ASSIGN),
     defaultTokenizer(TokenType.COMMA),
     defaultTokenizer(TokenType.SLASH),
diff --git a/smnp/token/type.py b/smnp/token/type.py
index 91b4811..c14d1c5 100644
--- a/smnp/token/type.py
+++ b/smnp/token/type.py
@@ -14,6 +14,7 @@ class TokenType(Enum):
     CLOSE_ANGLE = '>'
     SEMICOLON = ';'
     ASTERISK = '*'
+    PERCENT = '%'
     ASSIGN = '='
     ARROW = '->'
     COMMA = ','
@@ -44,7 +45,6 @@ class TokenType(Enum):
     AS = 'as'
     IDENTIFIER = 'identifier'
     COMMENT = 'comment'
-    PERCENT = 'percent'
 
     @property
     def key(self):