diff --git a/TODO b/TODO
index f6e3fb3..5c0e6e0 100644
--- a/TODO
+++ b/TODO
@@ -27,8 +27,6 @@ Tasks/Bugs:
 
 9.  regsub -all <exp> <string> <replace>
 
-10. [expr !<token>] {t/cmd_expr.t}
-
 11. add a glob compiler. (http://www.tcl.tk/man/tcl8.5/TclCmd/string.htm#M40)
      *, ?, [], \x (prior art: Tcl::Glob in core.) Needed for [string match]
      et al.
diff --git a/src/Partcl/Grammar.pm b/src/Partcl/Grammar.pm
index 8813f51..516199e 100644
--- a/src/Partcl/Grammar.pm
+++ b/src/Partcl/Grammar.pm
@@ -95,6 +95,7 @@ token int:sym<oct> { 0<[Oo]>? $<digits>=(<[0..7]>+) }
 # expression parsing
 
 INIT {
+    Partcl::Grammar.O(':prec<15>, :assoc<unary>', '%unary');
     Partcl::Grammar.O(':prec<13>', '%multiplicative');
     Partcl::Grammar.O(':prec<12>', '%additive');
     Partcl::Grammar.O(':prec<10>', '%compare_numeric');
@@ -125,6 +126,8 @@ token term:sym<false> {
 token term:sym<[ ]> { '[' ~ ']' <script> }
 token term:sym<" "> { '"' <quoted_atom>* '"' }
 
+token prefix:sym<!> { <sym> <O('%unary, :pirop<not>')> }
+
 token infix:sym<*> { <sym> <O('%multiplicative, :pirop<mul>')> }
 token infix:sym</> { <sym> <O('%multiplicative, :pirop<div>')> }