Minimal description of "use/no trace"

Author: lizmat

doc/Language/pragmas.pod6

@@ -115,7 +115,11 @@ before using them. You can relax this restriction with C<no>.
 =for code
     no strict; $x = 42; # OK
 
-=item X<B<trace>|trace> [TBD]
+=item X<B<trace>|trace>
+
+When C<use trace> is activated, any line of code executing will be written to
+STDERR.  You can use C<no trace> to switch off the feature, so this only happens
+for certain sections of code.
 
 =item X<B<v6>|v6> L<Writing Tests|/language/testing#Writing_tests>