diff --git a/CHANGELOG.md b/CHANGELOG.md
index 80f9dc7..7e48d6e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,7 +2,18 @@
 
 All notable changes to this project will be documented in this file. See [standard-version](https://github.com/conventional-changelog/standard-version) for commit guidelines.
 
-## [Unreleased](https://github.com/motdotla/dotenv-expand/compare/v11.0.7...master)
+## [Unreleased](https://github.com/motdotla/dotenv-expand/compare/v12.0.0...master)
+
+## [12.0.0](https://github.com/motdotla/dotenv-expand/compare/v11.0.7...v12.0.0) (2024-11-16)
+
+### Added
+
+* 🎉 support alternate value expansion ([#131](https://github.com/motdotla/dotenv-expand/pull/131))
+
+### Changed
+
+* 🎉 Expansion logic rewritten to match [dotenvx's](https://github.com/dotenvx/dotenvx). (*note: I recommend dotenvx over dotenv-expand when you are ready. I'm putting all my effort there for a unified standard .env implementation that works everywhere and matches bash, docker-compose, and more. In some cases it slightly improves on them. This leads to more reliability for your secrets and config.) ([#131](https://github.com/motdotla/dotenv-expand/pull/131))
+* ⚠️ BREAKING: do NOT expand in reverse order. Instead, order your .env file keys from first to last as they depend on each other for expansion - principle of least surprise. ([#131](https://github.com/motdotla/dotenv-expand/pull/131))
 
 ## [11.0.7](https://github.com/motdotla/dotenv-expand/compare/v11.0.6...v11.0.7) (2024-11-13)
 
diff --git a/lib/main.js b/lib/main.js
index e57074e..a893f79 100644
--- a/lib/main.js
+++ b/lib/main.js
@@ -1,79 +1,91 @@
 'use strict'
 
-// * /
-// *   (\\)?            # is it escaped with a backslash?
-// *   (\$)             # literal $
-// *   (?!\()           # shouldnt be followed by parenthesis
-// *   (\{?)            # first brace wrap opening
-// *   ([\w.]+)         # key
-// *   (?::-((?:\$\{(?:\$\{(?:\$\{[^}]*\}|[^}])*}|[^}])*}|[^}])+))? # optional default nested 3 times
-// *   (\}?)            # last brace warp closing
-// * /xi
-
-const DOTENV_SUBSTITUTION_REGEX = /(\\)?(\$)(?!\()(\{?)([\w.]+)(?::?-((?:\$\{(?:\$\{(?:\$\{[^}]*\}|[^}])*}|[^}])*}|[^}])+))?(\}?)/gi
-
 function _resolveEscapeSequences (value) {
   return value.replace(/\\\$/g, '$')
 }
 
-function interpolate (value, processEnv, parsed) {
-  return value.replace(DOTENV_SUBSTITUTION_REGEX, (match, escaped, dollarSign, openBrace, key, defaultValue, closeBrace) => {
-    if (escaped === '\\') {
-      return match.slice(1)
-    } else {
-      if (processEnv[key]) {
-        if (processEnv[key] === parsed[key]) {
-          return processEnv[key]
-        } else {
-          // scenario: PASSWORD_EXPAND_NESTED=${PASSWORD_EXPAND}
-          return interpolate(processEnv[key], processEnv, parsed)
-        }
-      }
+function expandValue (value, processEnv, runningParsed) {
+  const env = { ...runningParsed, ...processEnv } // process.env wins
 
-      if (parsed[key]) {
-        // avoid recursion from EXPAND_SELF=$EXPAND_SELF
-        if (parsed[key] !== value) {
-          return interpolate(parsed[key], processEnv, parsed)
-        }
-      }
+  const regex = /(?<!\\)\${([^{}]+)}|(?<!\\)\$([A-Za-z_][A-Za-z0-9_]*)/g
+
+  let result = value
+  let match
+  const seen = new Set() // self-referential checker
+
+  while ((match = regex.exec(result)) !== null) {
+    seen.add(result)
+
+    const [template, bracedExpression, unbracedExpression] = match
+    const expression = bracedExpression || unbracedExpression
+
+    // match the operators `:+`, `+`, `:-`, and `-`
+    const opRegex = /(:\+|\+|:-|-)/
+    // find first match
+    const opMatch = expression.match(opRegex)
+    const splitter = opMatch ? opMatch[0] : null
+
+    const r = expression.split(splitter)
+
+    let defaultValue
+    let value
+
+    const key = r.shift()
+
+    if ([':+', '+'].includes(splitter)) {
+      defaultValue = env[key] ? r.join(splitter) : ''
+      value = null
+    } else {
+      defaultValue = r.join(splitter)
+      value = env[key]
+    }
 
-      if (defaultValue) {
-        if (defaultValue.startsWith('$')) {
-          return interpolate(defaultValue, processEnv, parsed)
-        } else {
-          return defaultValue
-        }
+    if (value) {
+      // self-referential check
+      if (seen.has(value)) {
+        result = result.replace(template, defaultValue)
+      } else {
+        result = result.replace(template, value)
       }
+    } else {
+      result = result.replace(template, defaultValue)
+    }
 
-      return ''
+    // if the result equaled what was in process.env and runningParsed then stop expanding
+    if (result === processEnv[key] && result === runningParsed[key]) {
+      break
     }
-  })
+
+    regex.lastIndex = 0 // reset regex search position to re-evaluate after each replacement
+  }
+
+  return result
 }
 
 function expand (options) {
+  // for use with progressive expansion
+  const runningParsed = {}
+
   let processEnv = process.env
   if (options && options.processEnv != null) {
     processEnv = options.processEnv
   }
 
+  // dotenv.config() ran before this so the assumption is process.env has already been set
   for (const key in options.parsed) {
     let value = options.parsed[key]
 
-    const inProcessEnv = Object.prototype.hasOwnProperty.call(processEnv, key)
-    if (inProcessEnv) {
-      if (processEnv[key] === options.parsed[key]) {
-        // assume was set to processEnv from the .env file if the values match and therefore interpolate
-        value = interpolate(value, processEnv, options.parsed)
-      } else {
-        // do not interpolate - assume processEnv had the intended value even if containing a $.
-        value = processEnv[key]
-      }
+    // short-circuit scenario: process.env was already set prior to the file value
+    if (processEnv[key] && processEnv[key] !== value) {
+      value = processEnv[key]
     } else {
-      // not inProcessEnv so assume interpolation for this .env key
-      value = interpolate(value, processEnv, options.parsed)
+      value = expandValue(value, processEnv, runningParsed)
     }
 
     options.parsed[key] = _resolveEscapeSequences(value)
+
+    // for use with progressive expansion
+    runningParsed[key] = _resolveEscapeSequences(value)
   }
 
   for (const processKey in options.parsed) {
diff --git a/tests/.env.test b/tests/.env.test
index b5a602f..687588d 100644
--- a/tests/.env.test
+++ b/tests/.env.test
@@ -79,3 +79,6 @@ PASSWORD_EXPAND=${PASSWORD}
 PASSWORD_EXPAND_SIMPLE=$PASSWORD
 PASSWORD_EXPAND_NESTED=${PASSWORD_EXPAND}
 PASSWORD_EXPAND_NESTED_NESTED=${PASSWORD_EXPAND_NESTED}
+
+USE_IF_SET=true
+ALTERNATE=${USE_IF_SET:+alternate}
diff --git a/tests/main.js b/tests/main.js
index f8f7755..13a5e19 100644
--- a/tests/main.js
+++ b/tests/main.js
@@ -404,8 +404,8 @@ t.test('should expand with default value correctly', ct => {
 
   ct.equal(parsed.UNDEFINED_EXPAND_DEFAULT_SPECIAL_CHARACTERS, '/default/path:with/colon')
   ct.equal(parsed.UNDEFINED_EXPAND_DEFAULT_SPECIAL_CHARACTERS2, '/default/path:with/colon')
-  ct.equal(parsed.NO_CURLY_BRACES_UNDEFINED_EXPAND_DEFAULT_SPECIAL_CHARACTERS, '/default/path:with/colon')
-  ct.equal(parsed.NO_CURLY_BRACES_UNDEFINED_EXPAND_DEFAULT_SPECIAL_CHARACTERS2, '/default/path:with/colon')
+  ct.equal(parsed.NO_CURLY_BRACES_UNDEFINED_EXPAND_DEFAULT_SPECIAL_CHARACTERS, ':-/default/path:with/colon')
+  ct.equal(parsed.NO_CURLY_BRACES_UNDEFINED_EXPAND_DEFAULT_SPECIAL_CHARACTERS2, '-/default/path:with/colon')
 
   ct.end()
 })
@@ -454,7 +454,7 @@ t.test('handles two dollar signs', ct => {
   const dotenv = require('dotenv').config({ path: 'tests/.env.test', processEnv: {} })
   const parsed = dotenvExpand.expand(dotenv).parsed
 
-  ct.equal(parsed.TWO_DOLLAR_SIGNS, 'abcd$')
+  ct.equal(parsed.TWO_DOLLAR_SIGNS, 'abcd$$1234')
 
   ct.end()
 })
@@ -535,7 +535,7 @@ t.test('expands recursively', ct => {
   ct.end()
 })
 
-t.test('expands recursively reverse order', ct => {
+t.test('CANNOT expand recursively reverse order (ORDER YOUR .env file for least surprise)', ct => {
   const dotenv = {
     parsed: {
       BACKEND_API_HEALTH_CHECK_URL: '${MOCK_SERVER_HOST}/ci-health-check',
@@ -546,8 +546,8 @@ t.test('expands recursively reverse order', ct => {
   const parsed = dotenvExpand.expand(dotenv).parsed
 
   ct.equal(parsed.MOCK_SERVER_PORT, '8090')
-  ct.equal(parsed.MOCK_SERVER_HOST, 'http://localhost:8090')
-  ct.equal(parsed.BACKEND_API_HEALTH_CHECK_URL, 'http://localhost:8090/ci-health-check')
+  ct.equal(parsed.MOCK_SERVER_HOST, 'http://localhost:')
+  ct.equal(parsed.BACKEND_API_HEALTH_CHECK_URL, '/ci-health-check')
 
   ct.end()
 })
@@ -571,11 +571,30 @@ t.test('expands recursively but is smart enough to not attempt expansion of a pr
   const dotenv = require('dotenv').config({ path: 'tests/.env.test' })
   dotenvExpand.expand(dotenv)
 
+  ct.equal(process.env.PASSWORD, 'pas$word')
   ct.equal(process.env.PASSWORD_EXPAND, 'pas$word')
   ct.equal(process.env.PASSWORD_EXPAND_SIMPLE, 'pas$word')
-  ct.equal(process.env.PASSWORD, 'pas$word')
-  ct.equal(process.env.PASSWORD_EXPAND_NESTED, 'pas$word')
   ct.equal(process.env.PASSWORD_EXPAND_NESTED, 'pas$word')
+  ct.equal(process.env.PASSWORD_EXPAND_NESTED_NESTED, 'pas$word')
+
+  ct.end()
+})
+
+t.test('expands alternate logic', ct => {
+  const dotenv = require('dotenv').config({ path: 'tests/.env.test' })
+  dotenvExpand.expand(dotenv)
+
+  ct.equal(process.env.ALTERNATE, 'alternate')
+
+  ct.end()
+})
+
+t.test('expands alternate logic when not set', ct => {
+  process.env.USE_IF_SET = ''
+  const dotenv = require('dotenv').config({ path: 'tests/.env.test' })
+  dotenvExpand.expand(dotenv)
+
+  ct.equal(process.env.ALTERNATE, '')
 
   ct.end()
 })