@mixin keyframes($animation-name) {
    @-webkit-keyframes #{$animation-name} {
        @content;
    }
    @-moz-keyframes #{$animation-name} {
        @content;
    }
    @-ms-keyframes #{$animation-name} {
        @content;
    }
    @-o-keyframes #{$animation-name} {
        @content;
    }
    @keyframes #{$animation-name} {
        @content;
    }
}

@mixin animation($str) {
  -webkit-animation: #{$str};
  -moz-animation: #{$str};
  -ms-animation: #{$str};
  -o-animation: #{$str};
  animation: #{$str};
}

@include keyframes('menu-close', $var) {
  0% { right: 0%; }
  100% { right: $var; }
}

// usage

@include animation($ani-menu-close, -25px);