Doesn't need to be forward slashes (in either Perl or sed). In fact that last example I might write as either of the two following ways: s,$,/, s{$}{/

Doesn't need to be forward slashes (in either Perl or sed). In fact that last example I might write as either of the two following ways: s,$,/, s{$}{/} # this is supported in Perl but not sed to avoid having to escape the replacing character.