6.5.3 The Operators ~ and /~

The operator ~ can be used in the following ways:

list1 ~ list2

This tests whether list1 and list2 do congruate, this means, whether they have an element in common.

symbol1 ~ symbol2

This tests if atoms(symbol1) and atoms(symbol2), the lists of their atomic symbols, do congruate.

The comparison expr1 /~ expr2 holds iff the comparison expr1 ~ expr2 does not hold.