.placeholder(@lambda) {
    &::-webkit-input-placeholder { @lambda(); }
    &::-moz-placeholder { opacity: 1; @lambda(); }
    &:-ms-input-placeholder { @lambda(); }
    &:-moz-placeholder { opacity: 1; @lambda(); }
}

.placeholder(@property, @value) {
    .placeholder({ @{property}: @value; });
}