set debug= 'T';
select @@debug;
@@debug
T
set debug= '+P';
select @@debug;
@@debug
P:T
set debug= '-P';
select @@debug;
@@debug
T
#
# Bug #52629: memory leak from sys_var_thd_dbug in 
#  binlog.binlog_write_error
#
SET GLOBAL debug='d,injecting_fault_writing';
SELECT @@global.debug;
@@global.debug
d,injecting_fault_writing
SET GLOBAL debug='';
SELECT @@global.debug;
@@global.debug

End of 5.1 tests