Tcl-pTk-0.90/lib/Tcl/pTk.pm

 # Check to see if we are being called from Tcl::pTk::Callback, if so, then this is a valid 'break' call
 #   and we will die with _TK_BREAK_
 my @callInfo;

 die "_TK_BREAK_\n" if($callback);
 

Tcl-pTk-0.90/lib/Tcl/pTk/Widget.pm

                if {\$catchVal != 0} {
                        if { \$retVal != \"_TK_BREAK_\\n\" } { # BREAK returns are not errors
                                return -code error \$retVal

CERNEY/Tcl-pTk-0.90
Tk-804.033/Tk.pm

{
 die "_TK_BREAK_\n";
}

Tk-804.033/tkGlue.c

    }
   else if (!strcmp("_TK_BREAK_\n",s))
    {

       SvREFCNT_dec(what);
       croak("_TK_BREAK_\n");
      }

SREZIC/Tk-804.033