purpose | returns each item in the list, replacing within each title placeholders for filters, parameters and variables with their corresponding values |
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input | a selection of titles |

parameter | the `substitute` operator optionally accepts a variable number of parameters, see below for details |

output | the input titles with placeholders for filter expressions, parameter and variables replaced with their corresponding values |

Learn more about how to use Filters

The `substitute`

operator replaces any placeholders in the input titles in the following order:

- filter expressions
- parameters to the
`substitute`

operator - variables

placeholder syntax | description |

`$n$` | Text substitution of a parameter provided to the operator, where n is the position of the parameter starting with 1 for the first parameter. Unmatched placeholders pass through unchanged. |

`$(varname)$` | Text substitution of a variable. Undefined variables are replaced with an empty string. |

`${ filter expression }$` | Text substitution of the first result of evaluating a filter expression. In other words, if the filter returns multiple titles only the first one will be used. |