diff --git a/_repl.ts b/_repl.ts
new file mode 100644
index 0000000..01c2c6a
--- /dev/null
+++ b/_repl.ts
@@ -0,0 +1,132 @@
+import { align, embed, indent, undent } from "@okikio/undent";
+
+// · = space (shown explicitly to make indentation visible)
+// 1. Core — strip structural indent, keep relative indent
+// without undent
+console.log(`
+  Hello, world!
+    indented deeper
+  back to baseline
+`);
+//
+// ··Hello,·world!
+// ····indented·deeper
+// ··back·to·baseline
+//
+
+// with undent
+console.log(undent`
+  Hello, world!
+    indented deeper
+  back to baseline
+`);
+// Hello,·world!
+// ··indented·deeper
+// back·to·baseline
+
+// 2. align() — multi-line values stay at their insertion column
+const items = "- alpha\n- beta\n- gamma";
+// without align()
+console.log(undent`
+  list:
+    ${items}
+  end
+`);
+// list:
+// ··- alpha
+// - beta       ← snaps to column 0
+// - gamma
+// end
+
+// with align()
+console.log(undent`
+  list:
+    ${align(items)}
+  end
+`);
+// list:
+// ··- alpha
+// ··- beta     ← stays at insertion column
+// ··- gamma
+// end
+
+// 3. embed() — strip a value's own indent, then align it
+const sql = `
+    SELECT id, name
+    FROM   users
+    WHERE  active = true
+`;
+// without embed()
+console.log(undent`
+  query:
+    ${sql}
+`);
+// query:
+// ··
+// ····SELECT·id,·name   ← baked-in indent bleeds through
+// ····FROM···users
+// ····WHERE··active·=·true
+//
+
+// with embed()
+console.log(undent`
+  query:
+    ${embed(sql)}
+`);
+// query:
+// ··SELECT·id,·name
+// ··FROM···users
+// ··WHERE··active·=·true
+
+// 4. Indent anchor — explicit column-0 baseline
+// without anchor — content deeper than min indent keeps its relative offset
+console.log(undent`
+  if (ready) {
+    run();
+  }
+`);
+// if·(ready)·{
+// ··run();
+// }
+
+// with anchor — anchor column becomes column 0; content deeper than anchor keeps offset
+console.log(undent`
+  ${indent}
+    if (ready) {
+      run();
+    }
+`);
+// ··if·(ready)·{   ← 2 cols deeper than anchor, preserved
+// ····run();
+// ··}
+
+// 5. Newline fidelity — \r\n and \r pass through untouched
+const crlf = "A\r\nB\r\nC";
+// with undent + align — CRLF in values is never touched
+console.log(JSON.stringify(undent`prefix\n${align(crlf)}`));
+// "prefix\nA\r\nB\r\nC"
+
+// 6. Trim modes — per-side, fine-grained control
+// default: "all" — strips all blank wrapper lines
+console.log(JSON.stringify(undent`
+  hello
+`));
+// "hello"
+
+// "none" — keeps blank lines at both ends
+console.log(JSON.stringify(undent.with({ trim: "none" })`
+  hello
+`));
+// "\nhello\n"
+
+// "one" — strips at most one blank line from each end
+console.log(JSON.stringify(undent.with({ trim: "one" })`
+  hello
+`));
+// "hello"
+
+// per-side: keep leading blank, strip trailing
+console.log(JSON.stringify(undent.with({ trim: { leading: "none", trailing: "all" } })`
+  hello
+`));
+// "\nhello"