Error on scss file from Bootstrap

I'm building a quick landing page for a web site. I grabbed a sample landing page and implemented it on the site. This landing page uses a _variable.scss that is coming with the downloaded page from Bootstrap. I was getting an error when i tried to run npm run dev got an undefined expected identifier. Looking a VSC i saw that _variables.scss had 2 errors:

$carousel-control-icon-width:        20px !default;

$carousel-control-prev-icon-bg:      str-replace(url("data:image/svg+xml,%3csvg xmlns='http://www.w3.org/2000/svg' fill='#{$carousel-control-color}' viewBox='0 0 8 8'%3e%3cpath d='M5.25 0l-4 4 4 4 1.5-1.5-2.5-2.5 2.5-2.5-1.5-1.5z'/%3e%3c/svg%3e"), "#", "%23") !default;
$carousel-control-next-icon-bg:      str-replace(url("data:image/svg+xml,%3csvg xmlns='http://www.w3.org/2000/svg' fill='#{$carousel-control-color}' viewBox='0 0 8 8'%3e%3cpath d='M2.75 0l-1.5 1.5 2.5 2.5-2.5 2.5 1.5 1.5 4-4-4-4z'/%3e%3c/svg%3e"), "#", "%23") !default;

$-duration:       .6s !default;
$:    transform $-duration ease-in-out !default; // Define transform transition first if using multiple transitions (e.g., `transform 2s ease, opacity .5s ease-out`)


// Spinners

$spinner-width:         2rem !default;
$spinner-height:        $spinner-width !default;
$spinner-border-width:  .25em !default;

the errors are on:

$:    transform $-duration ease-in-out !default; // Define transform transition first if using multiple transitions (e.g., `transform 2s ease, opacity .5s ease-out`)

I don't think that $: is a valid parameter. Any ideas?