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$++ Identifier - mIRC
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Note: This feature has essentially been replaced by $+.$++ is a very old construct, similar to $+, which allowed to 'delay' the $+ behavior. A line :
" $+ $read c:\test.txt $++ "
can be found in the changelog of mIRC, suggesting that if that $++ were a $+, it would concatenate the filename to " before.
Nowadays, $++ is useless, it has theorically the same behavior as $+.
Compatibility
Added: mIRC v4.1
Added on: 27 Apr 1996
Note: Unless otherwise stated, this was the date of original functionality.
Further enhancements may have been made in later versions.