Variable name completion works like filename completion. If the parameter begins with a %, the completion routines will scan the environment, internal variables, and variable functions for matching variable names. For example, if the PROMPT and PATH variables are in the environment, in that order, and no other variables start with p, the sequence below may be used to display the value of PATH:

 

echo %p<Tab>

echo %PROMPT<Tab>

echo %PATH<Enter>