$varExists is used to safely check whether a temporary variable has been set before attempting to read it. Since $var returns an empty string for missing variables (silent failure), $varExists is the only reliable way to distinguish between “variable exists with an empty value” and “variable does not exist.”

Return Value

The return value is always the string "true" or "false" — not a boolean. Use string comparison in conditionals:

$if[$varExists[name]==true]
$if[$varExists[name]!=false]

Both forms work. $if[$varExists[name]] alone will always be truthy (non-empty string), so always compare explicitly.

Scope

This function only checks temporary variables created with $var. It does not check global or user-scoped variables — those would need to be checked by attempting $getVar and comparing the result.

Use Cases

• Lazy initialization: set a variable only if it hasn’t been set yet.
• Guard clauses: skip logic that depends on a variable being present.
• Debugging: verify that expected intermediate values are available.