In the below, I don't see why the x matches differently from the * ? 
#!/home/rir/rakudo/parrot_install/bin/perl6
use v6;

grammar Calc {
    rule TOP { <term> <op> <term>  }
#    rule TOP { <term>\s?<op>\s?<term>  }   # a fix
    token term { \d+(\.\d*)? }
    token op { '*' | 'x' }
}

my @t = (
    [ 44, " 8.8 * 5.0 " ],
    [ 44, " 8.8 x 5.0 " ],
    [ 44, " 8.8*5.0 " ],
    [ 44, " 8.8x5.0 " ],        # no match
);

for @t -> $i {
    my $m = Calc.parse( $i[1]);
    print $m ?? "  " !! "no";
    say " match: $i[1]"
}

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Be well,
rir

In reply to P6: parsing whitespace by rir

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