# The "=" is a scalar assignment operator, so:
# - f() is evaluated in scalar context.
# - The assignment returns $x.
my $x = f();

# The "=" is a list assignment operator, so:
# - f() is evaluated in list context.
# - The assignment returns ($x) in list context, or
# - the number of items returned by f() in scalar context.
my ($x) = f();