sub fiddle {
    my ($arg) = @_;
    $arg = "waffle";
}

sub faddle {
    my $arg = shift;
    $arg = "waffle";
}

sub muddle {
    $_[0] = "waffle";
}

my $value = "pancake";
print "$value\n"; # Prints "pancake"
fiddle($value);
print "$value\n"; # Prints "pancake"
faddle($value);
print "$value\n"; # Prints "pancake"
muddle($value);
print "$value\n"; # Prints "waffle"