Error compiling pike script

/www/luna.irc-hispano.org/admin/opers.pike:36	Error: Bad arguments to `+=().
/www/luna.irc-hispano.org/admin/opers.pike:36	Error: Expected: !function(!(object | mixed) ... : mixed) & function | function(int, int ... : int) | !function(!float ... : mixed) & function(int | float, int | float ... : float) | !function(!string ... : mixed) & function(string | int | float, string | int | float ... : string) | function((0=array), (1=array) ... : 0 | 1) | function((0=mapping), (1=mapping) ... : 0 | 1) | function((0=multiset), (1=multiset) ... : 0 | 1)
/www/luna.irc-hispano.org/admin/opers.pike:36	Error: Got     : function(array(string), string : array(string))