You only need the sigil during definition. So, for example (in the Perl 6 REPL):

    > my \x = 1
    1
    > my \y = 2
    2
    > say "Look Ma, no punctuation!" if x + y == 3
    Look Ma, no punctuation!

There are some implications of this; namely: x and y are now immutable. Back in the REPL:

    > my \x = 1
    1
    > x = 2
    Cannot modify an immutable Int (1)
      in block <unit> at <unknown file> line 1

This is because in Perl6 the sigil is a container for the value represented by that variable, so since you don't have a sigil, you don't have a container; that is: the names "x" and "y" are now literal synonyms for "1" and "2" (respectively). "x = 2" fails here for the same exact reason (and with the same exact error message) you'd get if you tried to do "1 = 2".