Control Flow
Control flow tags let you show or hide content based on conditions and repeat content for each item in a list.
TIP
For a tutorial-style introduction to these tags, see Conditional Logic.
If
Shows its content only when a condition is true. When the condition is false, the content stays out of the prompt entirely.
Properties
| Property | Type | Default | Description |
|---|---|---|---|
when | boolean | string | — | Boolean value, or a formula string starting with = |
provider | string | string[] | — | Show content only for these AI providers |
notProvider | string | string[] | — | Show content for all providers except these |
When you set multiple properties, pupt evaluates them in order: provider first, then notProvider, then when.
Boolean Conditions
Pass true or false directly:
<If when={true}>This content is included.</If>
<If when={false}>This content is excluded.</If>The first line includes its content. The second produces nothing.
Formula Conditions
You can use Excel-style formulas that start with =. Formulas can reference any variable created by an Ask tag:
<Ask.Number name="count" label="How many items?" default={3} silent />
<If when="=count>5">
Processing a large batch.
</If>Comparisons
<If when="=count>10">More than 10</If>
<If when="=count<=5">5 or fewer</If>
<If when="=name='Alice'">Hello, Alice!</If>String Comparisons
Use single quotes for strings inside formulas: =name='Alice', not =name="Alice".
Combining conditions
<If when="=AND(role='admin', status='active')">
Active admin content.
</If>
<If when="=OR(lang='en', lang='es')">
English or Spanish content.
</If>
<If when="=NOT(dryRun)">
Performing real operations.
</If>Math
<If when="=price*quantity>1000">
Large order detected.
</If>
<If when="=SUM(score1,score2,score3)>200">
High combined score.
</If>Text functions
<If when="=LEN(name)>0">
A name was provided.
</If>
<If when="=ISBLANK(optionalField)">
No optional field provided.
</If>HyperFormula, an Excel-compatible formula engine, powers these formulas. See the Conditionals Reference for the complete function list.
Provider Conditions
You can show content only when targeting a specific AI provider:
<If provider="anthropic">
Use XML tags to structure your response.
</If>
<If provider="openai">
Use markdown headers to structure your response.
</If>When you target Claude (Anthropic), only the first section appears. When you target GPT-4 (OpenAI), only the second appears.
You can also exclude a provider:
<If notProvider="openai">
This content appears for all providers except OpenAI.
</If>Supported providers: anthropic, openai, google, meta, mistral, deepseek, xai, cohere.
ForEach
Repeats content for each item in a list. You provide a function inside the tag that receives each item and returns the content to include.
Properties
| Property | Type | Default | Description |
|---|---|---|---|
items | array | (required) | Array of items to iterate over |
as | string | (required) | Name for the current item |
Example
<ForEach items={['bug fixes', 'improvements', 'style issues']} as="category">
{(category) => "- Review for " + category + "\n"}
</ForEach>Produces:
- Review for bug fixes
- Review for improvements
- Review for style issuesWhen the items list is empty, nothing appears in the output.
TIP
<ForEach> uses a function inside curly braces to generate content for each item. This is the one place where prompt files use a small bit of programming syntax.
Descriptive Conditionals
The tags below don't control what appears in the prompt -- they always produce output. They describe conditional behavior to the AI as structured instructions.
EdgeCases
Groups <When> tags that describe how the AI should handle unusual situations.
Properties
| Property | Type | Default | Description |
|---|---|---|---|
preset | 'standard' | 'minimal' | — | Use a preset set of edge cases |
extend | boolean | — | Add to a preset instead of replacing it |
delimiter | 'xml' | 'markdown' | 'none' | 'xml' | Delimiter style |
Examples
Custom edge cases:
<EdgeCases>
<When condition="input is empty" then="Return a helpful error message" />
<When condition="input contains special characters">
Sanitize the input before processing
</When>
</EdgeCases>Produces:
<edge-cases>
<when>
When input is empty: Return a helpful error message
</when>
<when>
When input contains special characters: Sanitize the input before processing
</when>
</edge-cases>Using a preset:
<EdgeCases preset="standard" />Produces:
<edge-cases>
When input is missing required data: Ask the user to provide the missing information
When request is outside your expertise: Acknowledge limitations and suggest alternative resources
When multiple valid interpretations exist: List the interpretations and ask for clarification
</edge-cases>The minimal preset includes a single case: "When input is unclear: Ask for clarification."
When
Describes a single conditional scenario. You typically use it inside <EdgeCases>.
Properties
| Property | Type | Default | Description |
|---|---|---|---|
condition | string | (required) | The situation description |
then | string | — | What to do (or use children instead) |
delimiter | 'xml' | 'markdown' | 'none' | 'xml' | Delimiter style |
Example
<When condition="the user provides no code"
then="ask them to paste the code they want reviewed" />Produces:
<when>
When the user provides no code: ask them to paste the code they want reviewed
</when>Fallbacks
Groups <Fallback> tags that describe what the AI should do when something goes wrong.
Properties
| Property | Type | Default | Description |
|---|---|---|---|
preset | 'standard' | — | Use the standard fallback preset |
extend | boolean | — | Add to a preset instead of replacing it |
delimiter | 'xml' | 'markdown' | 'none' | 'xml' | Delimiter style |
Examples
Custom fallbacks:
<Fallbacks>
<Fallback when="unable to find an answer"
then="Suggest related topics the user might explore" />
<Fallback when="question is outside your expertise"
then="Recommend a more appropriate resource" />
</Fallbacks>Produces:
<fallbacks>
<fallback>
If unable to find an answer, then Suggest related topics the user might explore
</fallback>
<fallback>
If question is outside your expertise, then Recommend a more appropriate resource
</fallback>
</fallbacks>Using a preset:
<Fallbacks preset="standard" />Produces:
<fallbacks>
If unable to complete the request, then explain why and suggest alternatives
If missing required information, then ask clarifying questions
If encountering an error, then describe the error and suggest a fix
</fallbacks>Fallback
Describes a single fallback behavior. You typically use it inside <Fallbacks>.
Properties
| Property | Type | Default | Description |
|---|---|---|---|
when | string | (required) | The error condition |
then | string | (required) | What to do |
delimiter | 'xml' | 'markdown' | 'none' | 'xml' | Delimiter style |
Quick Reference
| Tag | What it does |
|---|---|
<If when="=formula"> | Shows content when a formula is true |
<If when={true}> | Shows content when a value is true |
<If provider="anthropic"> | Shows content for a specific AI provider |
<If notProvider="openai"> | Shows content for all providers except one |
<ForEach> | Repeats content for each item in a list |
<EdgeCases> | Tells the AI how to handle unusual situations |
<When> | Tells the AI about a single edge case scenario |
<Fallbacks> | Tells the AI what to do when something fails |
<Fallback> | Tells the AI about a single fallback strategy |
Related
- Conditional Logic -- tutorial introduction
- Conditionals Reference -- complete formula function list
- Presets -- all available presets for edge cases and fallbacks