SCSS each

position.scss

  // Position all items absolute
  @each $pos in tl, tr, bl, br {
  	.pos-#{$pos} {
  		position:absolute;		
  	}
  }
  // Now position them
  .pos-tl{left:3%; top:3%;}
  .pos-tr{right:3%; top:3%;}
  .pos-bl{left:3%; bottom:3%;}
  .pos-br{right:3%; bottom:3%;}

For this case I'd probably suggest plain CSS could be easy to maintain rather than complex conditionals.

.pos-tl,pos-bl,pos-tr,pos-br {position:absolute; }
.pos-tl{left:3%; top:3%;}
.pos-tr{right:3%; top:3%;}
.pos-bl{left:3%; bottom:3%;}
.pos-br{right:3%; bottom:3%;}

Sweet thanks Anthony.