Function Syntax:
function:value Equal to value.
function:<=value Less than or equal to value.
function:<value Less than value.
function:=value Equal to value.
function:>value Greater than value.
function:>=value Greater than or equal to value.
function:start..end Is in the range of values from start to end.
function:start-end Is in the range of values from start to end.
But one of the most important ones is missing (in my opinion):
yup, it does the same.
Apparently !function:value works with all functions, while function:!value works not in all cases (but works well with strings as value).
So !function:value is more robust and this thread can be closed