Like we’ve mentioned on the gists page, variables are placeholders in prompt templates.

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Variable format

Gist variables are wrapped in double curly brackets: 
{{variable}}

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Variable names rules

The variable name must starts with a letter and can only contain lowercase letters, numbers, and underscores: 
{{1variable}} # ❌
{{variable-1}} # ❌
{{Variable-1}} # ❌
{{variable_1}} # ✅
{{variable1}} # ✅
In addition, there must be no spaces between the variable name and the curly brackets: 
{{ variable }} # ❌
{{variable}} # ✅