qmake function contains consider spaces but documentation does not mention about it

According to documentation

http://qt-project.org/doc/qt-4.8/qmake-function-reference.html#contains-variablename-value

function contains is searching substring in string.

But in reality the spaces are needed:

drivers = trr network raqqq
drivers2 = trrnetwork raqqq
contains( drivers, network ) = true
contains( drivers2, network ) = false

The documentation should be updated or the function fixed.