[instantiate].
'Command examples:       CHECK|: instantiate.'.
'                        CHECK|: instantiate int_Y_1.'.
'                        CHECK|: instantiate int_X_1 with x+1.'.
''.
'This command allows the user to instantiate a universal variable, to'.
'derive a specific instance of an unwrapped formula.'.
'These universal variables arise when universally quantified hypotheses,'.
'or existentially quantified conclusions, are unwrapped.'.
