Question

I was wondering. Are there languages that use only pass-by-reference as their eval strategy?

Answer 1

I don’t know what an “eval strategy” is, but Perl subroutine calls are pass-by-reference only.

sub change {
    $_[0] = 10;
}

$x = 5;
change($x);
print $x;  # prints "10"
change(0);  # raises "Modification of a read-only value attempted" error