__V

Also documented in context in the full Functions and Variables reference.

TL;DR: __V (Variable evaluation) resolves a dynamically built variable name — e.g. ${__V(row_${__counter(FALSE,)})} reads row_1, row_2, … — solving the “variable name that’s itself made of variables” problem that plain ${...} substitution can’t handle in one step.

The V (variable) function returns the result of evaluating a variable name expression. This can be used to evaluate nested variable references (which are not currently supported).

For example, if one has variables A1,A2 and N=1:

• \${A1} - works OK
• \${A\${N}} - does not work (nested variable reference)
• \${__V(A\${N})} - works OK. A\${N} becomes A1, and the __V function returns the value of A1

Name	Required	Description
Variable name	Yes	The variable to be evaluated.
Default value	No	The default value in case no variable found, if it’s empty and no variable found function returns the variable name

Example

${__V(row_${__counter(FALSE,)})}   → resolves to the value of row_1, row_2, ... as the counter increments

This pattern shows up whenever you’ve extracted multiple values with Match No. = -1 (producing var_1, var_2, …) and need to loop through them by a computed index — see __eval for the related “evaluate this string as an expression” function.

Related

• Functions and Variables Guide
• Regex Extractor Builder
• Correlation & Dynamic Values
• Full Functions Reference
• Component Reference