Template Syntax

Expressions are written inside double curly braces: {{expression}}. The behavior depends on whether the entire string is a single expression or contains mixed text and expressions.

Single expression

When the entire string is a single {{expression}}, the return type is preserved — it can be a number, boolean, array, object, or string.


{{price * quantity}}     → 50        (number)
{{age >= 18}}            → true      (boolean)
{{tags}}                 → ["a","b"] (array)
{{old.toUpperCase()}}    → "HELLO"   (string)

A single expression preserves the original type. This is important — {{"{{"}}42{{"}}"}} returns the number 42, not the string "42".

String interpolation

When the template contains text outside of {{...}}, or has multiple expressions, the result is always a string.


Hello {{firstName}}!                          → "Hello Alice!"
{{firstName}} {{lastName}}                    → "Alice Smith"
Total: {{price * quantity}} ({{currency}})    → "Total: 50 (USD)"

Each {{expression}} is evaluated independently, converted to a string, and interpolated into the surrounding text.

Error handling

When an expression fails to evaluate, it produces an error marker in the output:


{{unknownFunction()}}    → [ERROR: Not callable]
{{a +}}                  → [ERROR: Invalid expression]

For string interpolation with mixed expressions, only the failing expression is replaced with the error marker — the rest of the template still evaluates:


Name: {{firstName}}, Age: {{badExpr()}}
→ "Name: Alice, Age: [ERROR: Not callable]"

When an expression errors in Find & Replace, the replacement value becomes the error string [ERROR: ...]. Always test your expressions on a small sample first.

No-expression fallback

If a string has no {{...}} templates, it is treated as a plain literal:


hello world    → "hello world" (returned as-is)
42             → "42" (string, not number — no expression to evaluate)

Escaping

There is currently no escape syntax for literal {{ characters. If you need literal double braces in your output, they will be interpreted as expression delimiters.

Whitespace

Whitespace inside {{ }} is trimmed before evaluation:


{{ firstName }}       → same as {{firstName}}
{{  price * 2  }}     → same as {{price * 2}}