From Tapestries MUCK

subt

{subt:expr1,expr2}
{subt:expr1,expr2,expr3...}

Returns the difference of the values expr1 and expr2.

If more than two args are given, all values are subtracted from the first value in sequence.

For example:

{subt:10,3,2,4}

would be read as 10 - 3 - 2 - 4, and it would return a result of 1.