diff --git a/src/arg.sh b/src/arg.sh
index f01fd40..466ae79 100644
--- a/src/arg.sh
+++ b/src/arg.sh
@@ -18,7 +18,13 @@ arg::interpolate() {
    local -r arg="$1"
    local -r value="$2"
 
-   sed "s|<${arg}>|\"${value}\"|g"
+   local -r words="$(echo "$value" | wc -w | xargs)"
+
+   if [[ $words > 1 ]]; then
+      sed "s|<${arg}>|\"${value}\"|g"
+   else
+      sed "s|<${arg}>|${value}|g"
+   fi
 }
 
 arg::next() {
diff --git a/src/misc.sh b/src/misc.sh
index 27b8a70..669fcd7 100644
--- a/src/misc.sh
+++ b/src/misc.sh
@@ -9,18 +9,21 @@ command_exists() {
    type "$1" &> /dev/null
 }
 
+platform::existing_command() {
+   for cmd in "$@"; do
+      if command_exists "$cmd"; then
+         echo "$cmd"
+         return 0
+      fi
+   done
+   return 1
+}
+
 echoerr() {
    echo "$@" 1>&2
 }
 
 url::open() {
-   if command_exists xdg-open; then
-      xdg-open "$@"
-   elif command_exists open; then
-      open "$@"
-   elif command_exists google-chrome; then
-      google-chrome "$@"
-   elif command_exists firefox; then
-      firefox "$@"
-   fi
+   local -r cmd="$(platform::existing_command "${BROWSER:-}" xdg-open open google-chrome firefox)"
+   "$cmd" "$@"
 }
\ No newline at end of file
diff --git a/test/arg_test.sh b/test/arg_test.sh
new file mode 100644
index 0000000..6998cc0
--- /dev/null
+++ b/test/arg_test.sh
@@ -0,0 +1,18 @@
+#!/usr/bin/env bash
+
+interpolation_one_word() {
+   echo "curl http://mysite.com/<user>/profile" \
+    | arg::interpolate "user" "john" \
+    | test::equals "curl http://mysite.com/john/profile"
+}
+
+interpolation_multiple_words() {
+   echo "cp <file> <new_file>" \
+    | arg::interpolate "file" "C:/Program Files/app/foo.exe" \
+    | arg::interpolate "new_file" "/mnt/c/Users/john/foo.exe" \
+    | test::equals 'cp "C:/Program Files/app/foo.exe" /mnt/c/Users/john/foo.exe'
+}
+
+test::set_suite "arg"
+test::run "if there's only one word, interpolation doesn't include quotes" interpolation_one_word
+test::run "if there are multiple words, interpolation includes quotes" interpolation_multiple_words
diff --git a/test/platform_test.sh b/test/platform_test.sh
new file mode 100644
index 0000000..6443d8b
--- /dev/null
+++ b/test/platform_test.sh
@@ -0,0 +1,9 @@
+#!/usr/bin/env bash
+
+existing() {
+   platform::existing_command oasida fngo ni awk aoisdn oafm \
+    | test::equals awk
+}
+
+test::set_suite "platform"
+test::run "existing_command" existing