For MS-DOS conventions, allowed space or colon to split an option from a value.

E.g. Both of these are equivalent:

app /O:value

or

app /O value

Handling was also required for pure boolean options.

E.g.

No value specified, so "True" is assumed:

app /B

Specifying a boolean value directly:

app /B:false

Therefore, this must also be allowed:

app /B false

However, only valid boolean values are taken as the boolean option value:

app /B myfile.txt

"myfile.txt" is not the value of the /B option and will be treated as a positional parameter.