nested TimerHandlerEventProc? how is that even possible?

(gdb) bt
#0  0xb7e8cde6 in InfoFrameCmd (dummy=0x0, interp=0x8055770, objc=1, objv=0x8ece46c) at /home/colin/Desktop/packages/tcl8.6.1/generic/tclCmdIL.c:1174
#1  0xb7e734ef in Dispatch (data=0x8e8edb4, interp=0x8055770, result=0) at /home/colin/Desktop/packages/tcl8.6.1/generic/tclBasic.c:4335
#2  0xb7e78b4f in TclNRRunCallbacks (interp=interp@entry=0x8055770, result=0, rootPtr=rootPtr@entry=0x899a890) at /home/colin/Desktop/packages/tcl8.6.1/generic/tclBasic.c:4368
#3  0xb7e7c68f in TclEvalObjEx (interp=interp@entry=0x8055770, objPtr=objPtr@entry=0x8e8da30, flags=flags@entry=131072, invoker=invoker@entry=0x0, word=word@entry=0) at /home/colin/Desktop/packages/tcl8.6.1/generic/tclBasic.c:5934
#4  0xb7e7c6db in Tcl_EvalObjEx (interp=interp@entry=0x8055770, objPtr=0x8e8da30, flags=flags@entry=131072) at /home/colin/Desktop/packages/tcl8.6.1/generic/tclBasic.c:5915
#5  0xb7f54508 in AfterProc (clientData=0x8eecda8) at /home/colin/Desktop/packages/tcl8.6.1/generic/tclTimer.c:1191
#6  0xb7f54854 in TimerHandlerEventProc (evPtr=evPtr@entry=0x8435808, flags=flags@entry=-3) at /home/colin/Desktop/packages/tcl8.6.1/generic/tclTimer.c:593
#7  0xb7f31da3 in Tcl_ServiceEvent (flags=flags@entry=-3) at /home/colin/Desktop/packages/tcl8.6.1/generic/tclNotify.c:670
#8  0xb7f3203e in Tcl_DoOneEvent (flags=flags@entry=-3) at /home/colin/Desktop/packages/tcl8.6.1/generic/tclNotify.c:907
#9  0xb7ef12cc in Tcl_VwaitObjCmd (clientData=0x0, interp=0x8055770, objc=2, objv=0x805d0ec) at /home/colin/Desktop/packages/tcl8.6.1/generic/tclEvent.c:1408
#10 0xb7e734ef in Dispatch (data=0x899991c, interp=0x8055770, result=0) at /home/colin/Desktop/packages/tcl8.6.1/generic/tclBasic.c:4335
#11 0xb7e78b4f in TclNRRunCallbacks (interp=interp@entry=0x8055770, result=0, rootPtr=rootPtr@entry=0x8261ec0) at /home/colin/Desktop/packages/tcl8.6.1/generic/tclBasic.c:4368
#12 0xb7e7c68f in TclEvalObjEx (interp=interp@entry=0x8055770, objPtr=objPtr@entry=0x81b9ae0, flags=flags@entry=131072, invoker=invoker@entry=0x0, word=word@entry=0) at /home/colin/Desktop/packages/tcl8.6.1/generic/tclBasic.c:5934
#13 0xb7e7c6db in Tcl_EvalObjEx (interp=interp@entry=0x8055770, objPtr=0x81b9ae0, flags=flags@entry=131072) at /home/colin/Desktop/packages/tcl8.6.1/generic/tclBasic.c:5915
#14 0xb7f54508 in AfterProc (clientData=0x808fca0) at /home/colin/Desktop/packages/tcl8.6.1/generic/tclTimer.c:1191
#15 0xb7f54854 in TimerHandlerEventProc (evPtr=evPtr@entry=0x82544a0, flags=flags@entry=-3) at /home/colin/Desktop/packages/tcl8.6.1/generic/tclTimer.c:593
#16 0xb7f31da3 in Tcl_ServiceEvent (flags=flags@entry=-3) at /home/colin/Desktop/packages/tcl8.6.1/generic/tclNotify.c:670
#17 0xb7f320ea in Tcl_DoOneEvent (flags=flags@entry=-3) at /home/colin/Desktop/packages/tcl8.6.1/generic/tclNotify.c:971
#18 0xb7ef12cc in Tcl_VwaitObjCmd (clientData=0x0, interp=0x8055770, objc=2, objv=0x805ca30) at /home/colin/Desktop/packages/tcl8.6.1/generic/tclEvent.c:1408
#19 0xb7e734ef in Dispatch (data=0x81b9a84, interp=0x8055770, result=0) at /home/colin/Desktop/packages/tcl8.6.1/generic/tclBasic.c:4335
#20 0xb7e78b4f in TclNRRunCallbacks (interp=interp@entry=0x8055770, result=0, rootPtr=rootPtr@entry=0x0) at /home/colin/Desktop/packages/tcl8.6.1/generic/tclBasic.c:4368
#21 0xb7e78c7f in Tcl_EvalObjv (interp=interp@entry=0x8055770, objc=objc@entry=3, objv=objv@entry=0x805c8e0, flags=flags@entry=2097168) at /home/colin/Desktop/packages/tcl8.6.1/generic/tclBasic.c:4099
#22 0xb7e7a168 in TclEvalEx (interp=interp@entry=0x8055770, script=0x80b0808 "# Wuble.tcl - lighter Wub\nif {[info exists argv0] && ($argv0 eq [info script])} {\n    apply {{} {\n\tset home [file dirname [file normalize [info script]]]\n\tlappend ::auto_path $home [file join [file di"..., numBytes=4835, flags=flags@entry=0, line=1511, line@entry=1, clNextOuter=clNextOuter@entry=0x0, outerScript=0x80b0808 "# Wuble.tcl - lighter Wub\nif {[info exists argv0] && ($argv0 eq [info script])} {\n    apply {{} {\n\tset home [file dirname [file normalize [info script]]]\n\tlappend ::auto_path $home [file join [file di"...) at /home/colin/Desktop/packages/tcl8.6.1/generic/tclBasic.c:5237
#23 0xb7f25221 in Tcl_FSEvalFileEx (interp=interp@entry=0x8055770, pathPtr=pathPtr@entry=0x8082030, encodingName=0x0) at /home/colin/Desktop/packages/tcl8.6.1/generic/tclIOUtil.c:1809
#24 0xb7f2beab in Tcl_MainEx (argc=<optimised out>, argc@entry=2, argv=<optimised out>, argv@entry=0xbffff674, appInitProc=appInitProc@entry=0x8048790 <Tcl_AppInit>, interp=0x8055770) at /home/colin/Desktop/packages/tcl8.6.1/generic/tclMain.c:417
#25 0x0804868a in main (argc=2, argv=0xbffff674) at /home/colin/Desktop/packages/tcl8.6.1/unix/tclAppInit.c:84
(gdb)