the following operation converts $x from a Rat to a FatRat

That's a a mutable "container" aka a variable (a Scalar in this case) containing one immutable value (a Rat) then another immutable value (a FatRat). 

# Declare a new identifier $x and bind it to a new mutable Scalar cont
+ainer:
my $x;

# Assign a value into the Scalar:
$x                # An LHS reference to a Scalar returns the Scalar.
   =              # = is assignment. The LHS decides what to do with i
+t.
     9.9;         # Creates a new immutable Rat.

# VAR macro returns what the identifier is bound to:
say $x.VAR.^name; # Scalar -- the type of variable bound to $x.

# All other uses of $x or a Scalar on RHS return the value assigned in
+to the Scalar:
say $x;           # 9.9
say $x.^name;     # Rat -- the type of the value assigned into the Sca
+lar.
$x *= 2;          # This is equivalent to ...
$x = $x * 2;      # ... which assigns result of RHS expression into Sc
+alar on LHS.
say $x;           # 39.6

[download]

Hth.

In reply to Re^8: Small Perl 6 discoveries II, Rats by raiph
in thread [Perl6] Small discoveries I, __DATA__ by holli

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