run lsb test, or execute below commands:

1. copy test dir from tcl8.6.0 to target
2. run tests/expr.test
   
root@qemux86-64:~# tclsh /tmp/expr.test
...
...
...
==== expr-42.1 denormals FAILED
==== Contents of test case:

    expr 7e-324

---- Result was:
0.0
---- Result should have been (exact matching):
5e-324
==== expr-42.1 FAILED

expr.test:	Total	1866	Passed	1796	Skipped	49	Failed	21
Number of tests skipped for each constraint:
	5	!ieeeFloatingPoint
	8	longIs32bit
	5	testexprdoubleobj
	4	testexprdoubleobj&&ieeeFloatingPoint
	16	testexprlongobj
	11	testmathfunctions
root@qemux86-64:~#