diff --git a/src/domain.rs b/src/domain.rs
index cfa1899..0898b8b 100644
--- a/src/domain.rs
+++ b/src/domain.rs
@@ -1,26 +1,29 @@
 pub mod switch;
 
-#[derive(Debug, Clone, Eq)]
+#[derive(Debug, Clone, PartialEq, Eq)]
 struct Section {
     namespace: Option<String>,
     name: String,
 }
 
-impl<'a> From<&'a str> for Section {
-    fn from(s: &'a str) -> Self {
-        let (ns, name) = s
-            .trim()
-            .split_once(':')
-            .map_or_else(|| (None, s), |(ns, name)| (Some(ns), name));
+impl Section {
+    fn new(name: &str) -> Self {
         Self {
-            namespace: ns.map(String::from),
-            name: String::from(name),
+            name: name.to_string(),
+            namespace: None,
         }
     }
-}
 
-impl PartialEq for Section {
-    fn eq(&self, other: &Self) -> bool {
-        self.name == other.name && (self.namespace.is_none() || self.namespace == other.namespace)
+    fn with_namespace(namespace: &str, name: &str) -> Self {
+        Self {
+            name: name.to_string(),
+            namespace: Some(namespace.to_string()),
+        }
+    }
+
+    fn parse(s: &str) -> Self {
+        let s = s.trim();
+        s.split_once(':')
+            .map_or_else(|| Self::new(s), |(ns, name)| Self::with_namespace(ns, name))
     }
 }
diff --git a/src/domain/switch.rs b/src/domain/switch.rs
index 0f0089c..7c1df5e 100644
--- a/src/domain/switch.rs
+++ b/src/domain/switch.rs
@@ -35,14 +35,7 @@ where
     let choose_sections = req
         .sections
         .iter()
-        .map(|s| Section::from(s.as_str()))
-        .collect::<Vec<_>>();
-
-    dbg!(&choose_sections);
-
-    let choose_namespaces = choose_sections
-        .iter()
-        .map(|s| s.namespace.clone())
+        .map(|s| Section::parse(s.as_str()))
         .collect::<Vec<_>>();
 
     let mut current_sections: Option<Vec<Section>> = None;
@@ -55,11 +48,11 @@ where
             current_sections = section_info
                 .split_whitespace()
                 .next()
-                .map(|r| r.split(',').map(Section::from).collect());
+                .map(|r| r.split(',').map(Section::parse).collect());
             line.to_string()
         } else if let Some(cur_sections) = current_sections.clone() {
             let trimmed_line = line.trim_start_matches(['#', ' ']);
-            if cur_sections.iter().any(|s| choose_sections.contains(s)) {
+            if should_enable_variable(&choose_sections, &cur_sections) {
                 String::from(trimmed_line)
             } else {
                 format!("# {}", trimmed_line)
@@ -68,8 +61,6 @@ where
             line.to_string()
         };
 
-        dbg!(line, &current_sections, &new_line);
-
         writer
             .write_all(new_line.as_bytes())
             .map_err(|_| Error::WriteData)?;
@@ -82,6 +73,30 @@ fn is_section_end(line: &str) -> bool {
     line.trim().is_empty()
 }
 
+fn should_enable_variable(choose_sections: &[Section], current_sections: &[Section]) -> bool {
+    let cross_sections = choose_sections
+        .iter()
+        .filter(|s| {
+            s.namespace.is_some()
+                && current_sections
+                    .iter()
+                    .any(|s2| s.namespace == s2.namespace)
+        })
+        .collect::<Vec<_>>();
+
+    if cross_sections.is_empty() {
+        choose_sections.iter().any(|s| {
+            if s.namespace.is_none() {
+                current_sections.iter().any(|s2| s.name == s2.name)
+            } else {
+                current_sections.contains(s)
+            }
+        })
+    } else {
+        cross_sections.iter().any(|s| current_sections.contains(s))
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -133,4 +148,78 @@ mod tests {
             vec!["staging"],
         );
     }
+
+    #[test]
+    fn should_use_debug_in_staging_section() {
+        make_test(
+            BASE_ENV,
+            include_str!("../../test_data/should_use_debug_in_staging"),
+            vec!["staging", "debug:on"],
+        );
+    }
+
+    #[test]
+    fn should_use_staging_db_in_local_section() {
+        make_test(
+            BASE_ENV,
+            include_str!("../../test_data/should_use_staging_db_in_local"),
+            vec!["local", "db:staging"],
+        );
+    }
+
+    mod utils {
+        use super::*;
+
+        #[test]
+        fn should_not_enable_variables() {
+            assert!(!should_enable_variable(
+                &[Section::new("local")],
+                &[Section::new("staging")]
+            ));
+            assert!(!should_enable_variable(
+                &[Section::with_namespace("db", "local")],
+                &[Section::new("local")]
+            ));
+            assert!(!should_enable_variable(
+                &[Section::with_namespace("db", "local")],
+                &[Section::with_namespace("db", "staging")]
+            ));
+            assert!(!should_enable_variable(
+                &[
+                    Section::new("staging"),
+                    Section::with_namespace("debug", "on")
+                ],
+                &[
+                    Section::with_namespace("debug", "off"),
+                    Section::new("staging")
+                ]
+            ));
+        }
+
+        #[test]
+        fn should_enable_variables() {
+            assert!(should_enable_variable(
+                &[Section::new("local")],
+                &[Section::new("local")]
+            ));
+            assert!(should_enable_variable(
+                &[Section::new("local")],
+                &[Section::with_namespace("db", "local")]
+            ));
+            assert!(should_enable_variable(
+                &[Section::with_namespace("db", "local")],
+                &[Section::with_namespace("db", "local")]
+            ));
+            assert!(should_enable_variable(
+                &[
+                    Section::new("local"),
+                    Section::with_namespace("debug", "on")
+                ],
+                &[
+                    Section::with_namespace("debug", "on"),
+                    Section::new("staging")
+                ]
+            ));
+        }
+    }
 }