diff --git a/bashf/bashfile.py b/bashf/bashfile.py
index 454db1b..03b80d6 100644
--- a/bashf/bashfile.py
+++ b/bashf/bashfile.py
@@ -1,5 +1,9 @@
+import sys
 import os
 import json
+from random import randint
+
+import click
 
 from .bash import Bash
 
@@ -14,13 +18,60 @@ class TaskNotInBashfile(ValueError):
     pass
 
 
-class FlagNotAvailable(ValueError):
+class FilterNotAvailable(ValueError):
     pass
 
 
-class Flag:
-    def __init__(self, name):
-        self.name = name
+class TaskFilter:
+    def __init__(self, s):
+        self.source = s
+
+    def __str__(self):
+        return f"{self.source!r}"
+
+    @property
+    def name(self):
+        return self.source.split(":", 1)[0][len("@") :]
+
+    @property
+    def args(self):
+        args = {}
+
+        try:
+
+            for arg in self.source.split(":", 1)[1].split(":"):
+                split = arg.split("=", 1)
+
+                key = split[0]
+                value = split[1] if len(split) == 2 else True
+
+                args[key] = value
+        except IndexError:
+            pass
+
+        return args
+
+    def depends_on(self, **kwargs):
+        return []
+
+    @staticmethod
+    def execute_confirm(*, prompt=False, yes=False, secure=False, **kwargs):
+        if not yes:
+            if secure:
+                int1 = randint(0, 12)
+                int2 = randint(0, 12)
+
+                user_value = click.prompt(f"   What is {int1} times {int2}?")
+
+                if int(user_value) != int1 * int2:
+                    sys.exit(1)
+
+            else:
+                click.confirm("   Do you want to continue?", abort=True)
+
+    def execute(self, yes=False, **kwargs):
+        if self.name == "confirm":
+            self.execute_confirm(yes=yes, **self.args)
 
 
 class TaskScript:
@@ -34,6 +85,9 @@ class TaskScript:
     def __repr__(self):
         return f"<TaskScript name={self.name!r} depends_on={self.depends_on(recursive=True)!r}>"
 
+    def __str__(self):
+        return f"{self.name!r}"
+
     @property
     def declaration_line(self):
         for line in self.bashfile.source_lines:
@@ -41,21 +95,36 @@ class TaskScript:
                 return line
 
     def depends_on(self, *, reverse=False, recursive=False):
-        def gen_tasks():
-            task_names = self.declaration_line.split(":")[1].split()
-            task_indexes = [self.bashfile.find_chunk(task_name=n) for n in task_names]
-            for i in task_indexes:
-                yield TaskScript(bashfile=self.bashfile, chunk_index=i)
+        def gen_actions():
+            task_strings = self.declaration_line.split(":", 1)[1].split()
+            # Filter out filters.
+            # filters = [t for t in task_names if t.startswith("@")]
 
-        tasks = [t for t in gen_tasks()]
+            # for filter in filters:
+            # del task_names[task_names.index(filter)]
+
+            task_name_index_tuples = [
+                (self.bashfile.find_chunk(task_name=s), s) for s in task_strings
+            ]
+
+            for i, task_string in task_name_index_tuples:
+
+                if i is None:
+                    # Create the filter.
+                    yield TaskFilter(task_string)
+                else:
+                    # Otherwise, create the task.
+                    yield TaskScript(bashfile=self.bashfile, chunk_index=i)
+
+        actions = [t for t in gen_actions()]
 
         if recursive:
-            for i, task in enumerate(tasks[:]):
+            for i, task in enumerate(actions[:]):
                 for t in reversed(task.depends_on()):
-                    if t.name not in [task.name for task in tasks]:
-                        tasks.insert(i + 1, t)
+                    if t.name not in [task.name for task in actions]:
+                        actions.insert(i + 1, t)
 
-        return tasks
+        return actions
 
     @classmethod
     def _from_chunk_index(Class, bashfile, *, i):
@@ -68,7 +137,7 @@ class TaskScript:
             if line.startswith(indent_style):
                 return line[len(indent_style) :]
 
-    def execute(self, blocking=False):
+    def execute(self, *, blocking=False, **kwargs):
         bash = Bash(environ=self.bashfile.environ)
         return bash.command(self.source, blocking=False)
 
@@ -100,7 +169,7 @@ class TaskScript:
 class Bashfile:
     def __init__(self, *, path):
         self.path = path
-        self.environ = {}
+        self.environ = os.environ
         self._chunks = []
 
         if not os.path.exists(path):
diff --git a/bashf/cli.py b/bashf/cli.py
index 18c45ca..066b6c4 100644
--- a/bashf/cli.py
+++ b/bashf/cli.py
@@ -3,6 +3,8 @@ import click
 import crayons
 from .bashfile import Bashfile
 
+SAFE_ENVIRONS = ["HOME"]
+
 
 def indent(line):
     return f'{" " * 4}{line}'
@@ -35,6 +37,7 @@ def indent(line):
     multiple=True,
     help="task environment variable (can be passed multiple times).",
 )
+@click.option("--yes", is_flag=True, help="Set prompts to yes.")
 @click.option(
     "--fail",
     "-x",
@@ -42,6 +45,13 @@ def indent(line):
     type=click.BOOL,
     help="Fail immediately, if any task fails.",
 )
+@click.option(
+    "--secure",
+    "-s",
+    is_flag=True,
+    type=click.BOOL,
+    help="Ignore parent shell's environment variables.",
+)
 @click.option(
     "--arg",
     "-a",
@@ -59,7 +69,19 @@ def indent(line):
     help="environment variables, in JSON format.",
 )
 def task(
-    *, task, bashfile, arg, _list, environ, fail, environ_json, shellcheck, debug, quiet
+    *,
+    task,
+    bashfile,
+    arg,
+    _list,
+    environ,
+    fail,
+    environ_json,
+    shellcheck,
+    debug,
+    quiet,
+    secure,
+    yes,
 ):
     """bashf — Bashfile runner (the familiar Bash/Make hybrid)."""
     # Default to list behavior, when no task is provided.
@@ -70,6 +92,10 @@ def task(
 
     if bashfile == "__BASHFILE__":
         bashfile = Bashfile.find(root=".")
+    if secure:
+        for key in bashfile.environ:
+            if key not in SAFE_ENVIRONS:
+                del bashfile.environ[key]
 
     if environ_json:
         bashfile.add_environ_json(environ_json)
@@ -92,27 +118,33 @@ def task(
         try:
             task = bashfile[task]
         except KeyError:
-            click.echo(crayons.red(f"Task {task!r} does not exist!"))
+            click.echo(crayons.red(f"Task {task} does not exist!"))
             sys.exit(1)
 
-        def execute_task(task):
+        def execute_task(task, *, next_task=None):
             if not quiet:
                 click.echo(
                     crayons.white(" · ")
-                    + crayons.yellow(f"Executing task {task.name!r}")
-                    + crayons.white("…")
+                    + crayons.yellow(f"Executing {task}")
+                    + crayons.white(" · ")
                 )
-            return_code = task.execute()
+            return_code = task.execute(yes=yes, next_task=next_task)
 
             if fail:
                 if not return_code == 0:
-                    click.echo(f"Task {task.name!r} failed!")
+                    click.echo(f"Task {task} failed!")
                     sys.exit(return_code)
 
-        for task in task.depends_on(recursive=True) + [task]:
-            execute_task(task)
+        tasks = task.depends_on(recursive=True) + [task]
+        for task in tasks:
+            try:
+                next_task = tasks[tasks.index(task) + 1]
+            except IndexError:
+                next_task = None
 
-        click.echo(crayons.white(" · ") + crayons.green("Done") + crayons.white("!"))
+            execute_task(task, next_task=next_task)
+
+        click.echo(crayons.white(" · ") + crayons.green("Done") + crayons.white(" · "))
         sys.exit(0)
 
 
diff --git a/bashf/environment.py b/bashf/environment.py
new file mode 100644
index 0000000..e69de29
diff --git a/bashf/scripts/stdlib.sh b/bashf/scripts/stdlib.sh
index 1e82d39..3106096 100644
--- a/bashf/scripts/stdlib.sh
+++ b/bashf/scripts/stdlib.sh
@@ -10,3 +10,37 @@ fi
 bashf-indent() {
     bashf-sed "s/^/    /"
 }
+
+# ---------------------
+# From: https://github.com/heroku/buildpack-stdlib/blob/master/stdlib.sh
+
+# Buildpack Steps.
+puts_step() {
+    if [[ "$*" == "-" ]]; then
+        read -r output
+    else
+        output=$*
+    fi
+    echo -e "\\e[1m\\e[36m=== $output\\e[0m"
+    unset output
+}
+
+# Buildpack Error.
+puts_error() {
+    if [[ "$*" == "-" ]]; then
+        read -r output
+    else
+        output=$*
+    fi
+    echo -e "\\e[1m\\e[31m=!= $output\\e[0m"
+}
+
+# Buildpack Warning.
+puts_warn() {
+    if [[ "$*" == "-" ]]; then
+        read -r output
+    else
+        output=$*
+    fi
+    echo -e "\\e[1m\\e[33m=!= $output\\e[0m"
+}