diff --git a/src/Seq.php b/src/Seq.php
new file mode 100644
index 0000000..0f40c93
--- /dev/null
+++ b/src/Seq.php
@@ -0,0 +1,108 @@
+<?php
+
+namespace ipl\Stdlib;
+
+/**
+ * Collection of utilities for traversables
+ */
+class Seq
+{
+    /**
+     * Check if the traversable contains the given needle
+     *
+     * @param array|iterable $traversable
+     * @param mixed $needle Might also be a closure
+     * @param bool $caseSensitive Whether strings should be compared case-sensitive
+     *
+     * @return bool
+     */
+    public static function contains($traversable, $needle, $caseSensitive = true)
+    {
+        return self::find($traversable, $needle, $caseSensitive)[0] !== null;
+    }
+
+    /**
+     * Search in the traversable for the given needle and return its key and value
+     *
+     * @param array|iterable $traversable
+     * @param mixed $needle Might also be a closure
+     * @param bool $caseSensitive Whether strings should be compared case-sensitive
+     *
+     * @return array An array with two entries, the first is the key, then the value. Both are null if nothing is found.
+     */
+    public static function find($traversable, $needle, $caseSensitive = true)
+    {
+        $usesCallback = is_callable($needle);
+        if (! $usesCallback && $caseSensitive && is_array($traversable)) {
+            return [array_search($needle, $traversable, true), $needle];
+        }
+
+        if (! $caseSensitive && is_string($needle) && ! $usesCallback) {
+            $needle = strtolower($needle);
+        }
+
+        foreach ($traversable as $key => $item) {
+            $originalItem = $item;
+            if (! $caseSensitive && is_string($item)) {
+                $item = strtolower($item);
+            }
+
+            if ($usesCallback && $needle($item)) {
+                return [$key, $originalItem];
+            } elseif ($item === $needle) {
+                return [$key, $originalItem];
+            }
+        }
+
+        return [null, null];
+    }
+
+    /**
+     * Search in the traversable for the given needle and return its key
+     *
+     * @param array|iterable $traversable
+     * @param mixed $needle Might also be a closure
+     * @param bool $caseSensitive Whether strings should be compared case-sensitive
+     *
+     * @return mixed|null Null if nothing is found
+     */
+    public static function findKey($traversable, $needle, $caseSensitive = true)
+    {
+        return self::find($traversable, $needle, $caseSensitive)[0];
+    }
+
+    /**
+     * Search in the traversable for the given needle and return its value
+     *
+     * @param array|iterable $traversable
+     * @param mixed $needle Might also be a closure
+     * @param bool $caseSensitive Whether strings should be compared case-sensitive
+     *
+     * @return mixed|null Null if nothing is found
+     */
+    public static function findValue($traversable, $needle, $caseSensitive = true)
+    {
+        $usesCallback = is_callable($needle);
+        if (! $usesCallback && $caseSensitive && is_array($traversable)) {
+            return isset($traversable[$needle]) ? $traversable[$needle] : null;
+        }
+
+        if (! $caseSensitive && is_string($needle) && ! $usesCallback) {
+            $needle = strtolower($needle);
+        }
+
+        foreach ($traversable as $key => $item) {
+            if (! $caseSensitive && is_string($key)) {
+                $key = strtolower($key);
+            }
+
+            if ($usesCallback && $needle($key)) {
+                return $item;
+            } elseif ($key === $needle) {
+                return $item;
+            }
+        }
+
+        return null;
+    }
+}
diff --git a/tests/SeqTest.php b/tests/SeqTest.php
new file mode 100644
index 0000000..3028dd5
--- /dev/null
+++ b/tests/SeqTest.php
@@ -0,0 +1,90 @@
+<?php
+
+namespace ipl\Tests\Stdlib;
+
+use ArrayIterator;
+use ipl\Stdlib\Seq;
+
+class SeqTest extends TestCase
+{
+    public function testFindWithArrays()
+    {
+        $this->assertEquals(
+            ['oof', 'BAR'],
+            Seq::find(['foo' => 'bar', 'oof' => 'BAR'], 'BAR')
+        );
+        $this->assertEquals(
+            ['foo', 'bar'],
+            Seq::find(['foo' => 'bar', 'oof' => 'BAR'], 'BAR', false)
+        );
+    }
+
+    public function testFindWithGenerators()
+    {
+        $generatorCreator = function () {
+            yield 'foo' => 'bar';
+            yield 'oof' => 'BAR';
+        };
+
+        $this->assertEquals(
+            ['oof', 'BAR'],
+            Seq::find($generatorCreator(), 'BAR')
+        );
+        $this->assertEquals(
+            ['foo', 'bar'],
+            Seq::find($generatorCreator(), 'BAR', false)
+        );
+    }
+
+    public function testFindWithIterators()
+    {
+        $this->assertEquals(
+            ['oof', 'BAR'],
+            Seq::find(new ArrayIterator(['foo' => 'bar', 'oof' => 'BAR']), 'BAR')
+        );
+        $this->assertEquals(
+            ['foo', 'bar'],
+            Seq::find(new ArrayIterator(['foo' => 'bar', 'oof' => 'BAR']), 'BAR', false)
+        );
+    }
+    public function testFindValueWithArrays()
+    {
+        $this->assertEquals(
+            'BAR',
+            Seq::findValue(['foo' => 'bar', 'FOO' => 'BAR'], 'FOO')
+        );
+        $this->assertEquals(
+            'bar',
+            Seq::findValue(['foo' => 'bar', 'FOO' => 'BAR'], 'FOO', false)
+        );
+    }
+
+    public function testFindValueWithGenerators()
+    {
+        $generatorCreator = function () {
+            yield 'foo' => 'bar';
+            yield 'FOO' => 'BAR';
+        };
+
+        $this->assertEquals(
+            'BAR',
+            Seq::findValue($generatorCreator(), 'FOO')
+        );
+        $this->assertEquals(
+            'bar',
+            Seq::findValue($generatorCreator(), 'FOO', false)
+        );
+    }
+
+    public function testFindValueWithIterators()
+    {
+        $this->assertEquals(
+            'BAR',
+            Seq::findValue(new ArrayIterator(['foo' => 'bar', 'FOO' => 'BAR']), 'FOO')
+        );
+        $this->assertEquals(
+            'bar',
+            Seq::findValue(new ArrayIterator(['foo' => 'bar', 'FOO' => 'BAR']), 'FOO', false)
+        );
+    }
+}