Update:

The last case I mentioned in my previous post, the condition has to be 3 tokens, the third token has to return $null while the second token has to return $true or $false.

For example:

Code
//if (a $true %var) echo -ag true $v1 | else echo -ag ok $v1
or
//if (a $($true) $null) echo -ag true $v1 | else echo -ag ok $v1
or 
//if (a $true $+($null)) echo -ag true $v1 | else echo -ag ok $v1
With the exact same rules, if $true or $false is $null instead, mIRC report an empty unknown operator error, maybe having a literal $null as the unknown operator would help.

Also found that mIRC does not choke when the count of '(' and ')' becomes negative, which is really error prone:
Code
//if ) { echo -a ok }
//if (1) && ) { echo -a ok }
Shouldn't that be fixed? I don't see any reason to keep such compatibility.

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