Generally, Tyl programmers try to avoid parentheses as much as posible.
But at times, it is a must or convenient, to use parentheses, when it is needed to construct a contained statement.

As shown in Assignment of Multiple Scalar Variables, Tyl Statement Composition and Variable Condition pages, these statements can be interpreted correctly:
numa numb 21
num len 'Kilimanjaro'
esverdad ? print 'Si' \ print 'No'
The above code with parentheses:
numa ( numb 21 )
num ( len 'Kilimanjaro' )
esverdad ? ( print 'Si' ) \ ( print 'No')
All runs fine as well, and if it helps you, put parentheses to clarify the code.

The times where it is a must to use parentheses arise when not using them will cause ambiguity or failure to your code.

In variable assignment by ternary statement:
num ( isvalid ? 1 \ -1 )
Omitting the parentheses will cause the system to treat num isvalid, as a condition statement.
But with parentheses, the ternary statement isvalid ? 1 \ 1, will be the source of the assignment to num.

In list position by statement:
names 'Tony' 'Carla' 'Ron'
ind 0
name names ( ind ++ )
Omitting the parentheses will cause the system to treat ind itself as the position, and will try to treat '++', as the value to set in that position unsuccessfully.
But with parentheses, the increment statement 'ind ++', will cause ind to be incremented to 1, and this will be the position for names list, eventually leading to the assignment of the second item of names to name.

In function parameter by statement:
place 'Puerto Montt'
placetypes 'Country' 'City' 'Street'
getplacetitle ( placetypes 1 ) place
getplacetitle type place: print type + ': ' + place
getplacetitle function has type and place parameters, and it constructs a title in the format 'type: place'.
Omitting the parentheses will cause the system to treat placetypes list as the place type string, which is wrong.
But with parentheses, the list access statement placetypes 1, will be the source to the place type parameter, thus giving to getplacetitle the parameters 'City' and 'Puerto Montt', and it will construct the string 'City: Puerto Montt'.

Though it might be tempting to use parentheses vastly, Tyl is limited in this sense, and apart from the above mentioned scenarios, try to avoid them.