Eval & the REPL

Eval evaluates an AHK expression in the caller's live scope. The REPL keeps that state across multiple inputs.

Opt into Eval

#Requires AutoHotkey v2.1-alpha.31
#EnableEval
count := 21
Print(Eval("count * 2"))

Expected output: 42. Enable evaluation with #EnableEval or the /Eval launch flag. Invalid expressions throw SyntaxError; unresolved identifiers can throw UnsetError. Evaluation can call functions and mutate state, so it is code execution, not a sandbox for untrusted expressions.

Explore interactively

ahk repl
>>> value := 10
10
>>> value * 4
40
>>> .help
>>> .exit

Only .help and .exit are documented meta-commands here. repl script.ahk runs the script's auto-execute section before opening a session against its state. Timers and GUI events can continue running.

Machine-readable sessions

"value := 21`nvalue * 2`n.exit" | ahk /Diag=json repl

JSON mode emits result records on stdout, including recoverable failures, blank lines, and meta-commands. Ordinary script output is redirected to stderr in this mode so it does not break result framing. Explicit ExitApp or a fatal process failure can end the session before a reply.

In ClautoHotkey

Use /ahk-eval for REPL-focused work. Ask for bounded expressions and preserved stdout/stderr. A session makes exploratory work fast; a saved assertion test makes the result repeatable.