separator used for the output list is the same as the one used for the
input, but a separator setting is not included in the output. For example:
.code
-${filter{a:b:c}{!eq{$item}{b}}
+${filter{a:b:c}{!eq{$item}{b}}}
.endd
yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored
to what it was before. See also the &*map*& and &*reduce*& expansion items.