Value of properties can be expression.

Example found in the 2007.03 Liberty Reference Manual that was also found
in the wild:

    input_voltage(CMOS) {
        vil : 0.3 * VDD ;
        vih : 0.7 * VDD ;
        vimin : -0.5 ;
        vimax : VDD + 0.5 ;
    }

Current implementation just parses the expression but no interpretation is done.

src/map/scl/sclLiberty.c

@@ -399,6 +399,18 @@ int Scl_LibertyBuildItem( Scl_Tree_t * p, char ** ppPos, char * pEnd )
         if ( Scl_LibertySkipSpaces( p, ppPos, pEnd, 1 ) )
             goto exit;
         pNext = *ppPos;
+        while ( *pNext == '+' || *pNext == '-' || *pNext == '*' || *pNext == '/' )
+        {
+        (*ppPos) += 1;
+            if ( Scl_LibertySkipSpaces( p, ppPos, pEnd, 0 ) )
+                goto exit;
+            if ( Scl_LibertySkipEntry( ppPos, pEnd ) )
+                goto exit;
+            Head.End = *ppPos - p->pContents;
+            if ( Scl_LibertySkipSpaces( p, ppPos, pEnd, 1 ) )
+                goto exit;
+        pNext = *ppPos;
+        }
         if ( *pNext != ';' && *pNext != '\n' )
             goto exit;
         *ppPos = pNext + 1;