+sub make_symbol { Data::SExpression::Symbol->new(shift) }
+
+# types
+our $LIST = make_symbol 'LIST';
+our $SYMBOL = make_symbol 'SYMBOL';
+our $VAR = make_symbol 'VAR';
+# no need for closures
+our $PROC = make_symbol 'PROC';
+our $IF = make_symbol 'IF';
+our $CALL = make_symbol 'CALL';
+# no need for quoted constants
+
+# primitives
+our $MORE = make_symbol 'MORE';
+our $FUNCALL = make_symbol 'FUNCALL';
+