try this

denow

@@ -1,7 +1,6 @@
 #!/bin/sh
 set -e
 deno_version="$__DENO_VERSION__"
-# https://stackoverflow.com/questions/29832037/how-to-get-script-directory-in-posix-sh
 dir=$(CDPATH='' cd -- "$(dirname -- "$0")" && pwd)
 if [ ! -d "$dir/.deno" ]; then
   if ! o=$(curl -fsSL https://deno.land/install.sh | DENO_INSTALL="$dir/.deno" sh -s "v$deno_version" 2>&1); then

install.sh

@@ -7,10 +7,12 @@ else
   base_url='https://deno.land/x/denow/'
 fi
 
-if [ "$OS" = "Windows_NT" ]; then
-  pwsh -Command "v='$1'; irm ${DENOW_DL_BASE_URL}/install.ps1 | iex"
-  exit 0
-fi
+# https://gist.github.com/lukechilds/a83e1d7127b78fef38c2914c4ececc3c
+get_latest_release() {
+  curl --silent "https://api.github.com/repos/$1/releases/latest" | # Get latest release from GitHub api
+    grep '"tag_name":' |                                            # Get tag line
+    sed -E 's/.*"([^"]+)".*/\1/'                                    # Pluck JSON value
+}
 
 if command -v curl 2> /dev/null; then
   curl -fsSL "${base_url}denow.bat" -o ./denow.bat
@@ -27,8 +29,7 @@ chmod +x ./denow
 if [ -n "$1" ]; then
   deno_version="$1"
 elif command -v grep 2> /dev/null; then
-  # https://gist.github.com/lukechilds/a83e1d7127b78fef38c2914c4ececc3c
-  deno_version=$(curl --silent "https://api.github.com/repos/denoland/deno/releases/latest" | grep -Po "(?<=\"tag_name\": \"v).*(?=\")")
+  deno_version=$(get_latest_release denoland/deno)
 else
   echo "Unable to fetch latest version" >&2
   exit 1