[As of 8.4, add "-DPURIFY" to CFLAGS to change core allocation from pool- to single-object-allocation. tclguy might change the label someday.]
[... -DTCL_MEM_DEBUG ...]
If you're using tclsh or another shell driven by Tcl_Main(), and you're using Tcl 8.4a4 or later, then you can reduce the number of memory leak false alarms by ending your script with:
proc exit args {}