Improve grammar

Per suggestion by oodler577 in #18736.

With correction reported as needed by grinnz in
#18806.

pod/perlnumber.pod

@@ -128,11 +128,11 @@ used may lead to breakage of some of the above rules.
 
 =head1 Flavors of Perl numeric operations
 
-Perl operations which take a numeric argument treat that argument in one
-of four different ways: they may force it to one of the integer/floating/
-string formats, or they may behave differently depending on the format of
-the operand.  Forcing a numeric value to a particular format does not
-change the number stored in the value.
+Perl operations which take a numeric argument treat that argument in one of
+four different ways: they may force it to one of the integer, floating, or
+string formats; or they may behave differently depending on the format of the
+operand.  Forcing a numeric value to a particular format does not change the
+number stored in the value.
 
 All the operators which need an argument in the integer format treat the
 argument as in modular arithmetic, e.g., C<mod 2**32> on a 32-bit