Simplify control flow ("return is the best if")

bin/dissect_url

 main() {
     local Url=$1
     local i=0
-    if [[ -n "$Url" ]]; then
+    test -n "$Url" \
+     && dissect \
+     && return 0
+    while read -r Url;
+    do
+        ((i++))
+        printf '=== url %02d =============================================\n' $i
         dissect
-    else
-        while read -r Url;
-        do
-            ((i++))
-            printf '=== url %02d =============================================\n' $i
-            dissect
-        done
-    fi
+    done
 }
 
 main "$@"