diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..ca25cbb
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2018 Sergey Grebenshchikov
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
\ No newline at end of file
diff --git a/Makefile b/Makefile
index 2bf27aa..8267474 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,4 @@
-VERSION = 1.0.1
+VERSION = 1.1.0
 
 APP      := subst
 PACKAGES := $(shell go list -f {{.Dir}} ./...)
diff --git a/README.md b/README.md
index c7e5eaf..56fe224 100644
--- a/README.md
+++ b/README.md
@@ -23,16 +23,16 @@ Or [download the binary](https://github.com/sgreben/subst/releases/latest) from
 
 ```bash
 # Linux
-curl -LO https://github.com/sgreben/subst/releases/download/1.0.1/subst_1.0.1_linux_x86_64.zip
-unzip subst_1.0.1_linux_x86_64.zip
+curl -LO https://github.com/sgreben/subst/releases/download/1.1.0/subst_1.1.0_linux_x86_64.zip
+unzip subst_1.1.0_linux_x86_64.zip
 
 # OS X
-curl -LO https://github.com/sgreben/subst/releases/download/1.0.1/subst_1.0.1_osx_x86_64.zip
-unzip subst_1.0.1_osx_x86_64.zip
+curl -LO https://github.com/sgreben/subst/releases/download/1.1.0/subst_1.1.0_osx_x86_64.zip
+unzip subst_1.1.0_osx_x86_64.zip
 
 # Windows
-curl -LO https://github.com/sgreben/subst/releases/download/1.0.1/subst_1.0.1_windows_x86_64.zip
-unzip subst_1.0.1_windows_x86_64.zip
+curl -LO https://github.com/sgreben/subst/releases/download/1.1.0/subst_1.1.0_windows_x86_64.zip
+unzip subst_1.1.0_windows_x86_64.zip
 ```
 
 ## Use it
@@ -90,6 +90,13 @@ $SHELL
 /bin/zsh
 ```
 
+To ignore occurrences of defined variables, you can define an escape string using the `-escape` flag:
+
+```shell
+$ echo 'unescaped: $X, ${X}. escaped: \$X, \${X}.' | subst -escape '\' X=value
+unescaped: value, value. escaped: \$X, \${X}.
+```
+
 ## Comments
 
 Feel free to [leave a comment](https://github.com/sgreben/subst/issues/1) or create an issue.
diff --git a/README.template.md b/README.template.md
index 6d3917b..452c55b 100644
--- a/README.template.md
+++ b/README.template.md
@@ -90,6 +90,13 @@ $SHELL
 /bin/zsh
 ```
 
+To ignore occurrences of defined variables, you can define an escape string using the `-escape` flag:
+
+```shell
+$ echo 'unescaped: $X, ${X}. escaped: \$X, \${X}.' | subst -escape '\' X=value
+unescaped: value, value. escaped: \$X, \${X}.
+```
+
 ## Comments
 
 Feel free to [leave a comment](https://github.com/sgreben/subst/issues/1) or create an issue.
\ No newline at end of file
diff --git a/expand.go b/expand.go
new file mode 100644
index 0000000..b763f63
--- /dev/null
+++ b/expand.go
@@ -0,0 +1,77 @@
+package main
+
+// Modified copy of os/env.go. The Go LICENSE file is included below:
+
+// Copyright (c) 2009 The Go Authors. All rights reserved.
+
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+
+//    * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//    * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//    * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+func expand(s, escape string, mapping func(string) string) string {
+	buf := make([]byte, 0, 2*len(s))
+	i := 0
+	shouldEscape := len(escape) > 0
+	escaped := escape + "$"
+	for j := 0; j < len(s); j++ {
+		if shouldEscape {
+			if j+len(escaped) < len(s) && s[j:j+len(escaped)] == escaped {
+				j += len(escaped)
+				continue
+			}
+		}
+		if s[j] == '$' && j+1 < len(s) {
+			buf = append(buf, s[i:j]...)
+			name, w := variableName(s[j+1:])
+			buf = append(buf, mapping(name)...)
+			j += w
+			i = j + 1
+		}
+	}
+	return string(buf) + s[i:]
+}
+
+func isAlphaNum(c uint8) bool {
+	return c == '_' || '0' <= c && c <= '9' || 'a' <= c && c <= 'z' || 'A' <= c && c <= 'Z'
+}
+
+func variableName(s string) (string, int) {
+	if s[0] == '{' {
+		for i := 1; i < len(s); i++ {
+			if s[i] == '}' {
+				return s[1:i], i + 1
+			}
+		}
+		return "", 1
+	}
+	var i int
+	for i = 0; i < len(s) && isAlphaNum(s[i]); i++ {
+	}
+	return s[:i], i
+}
diff --git a/main.go b/main.go
index ff658d0..17c478b 100644
--- a/main.go
+++ b/main.go
@@ -14,15 +14,18 @@ var definitions = make(map[string]string)
 var nonzeroExit = false
 var newline = []byte{'\n'}
 
-var quiet bool
-var unknownWarn = true
-var unknownKey = enumVar{
-	Choices: []string{
-		unknownValueEmpty,
-		unknownValueIgnore,
-		unknownValueError,
-	},
-}
+var (
+	quiet       bool
+	unknownWarn = true
+	escape      string
+	unknownKey  = enumVar{
+		Choices: []string{
+			unknownValueEmpty,
+			unknownValueIgnore,
+			unknownValueError,
+		},
+	}
+)
 
 const (
 	unknownValueEmpty  = "empty"
@@ -43,6 +46,7 @@ func parseDefinition(d string) (key, value string, err error) {
 func init() {
 	log.SetOutput(os.Stderr)
 	flag.BoolVar(&quiet, "q", false, "suppress all logs")
+	flag.StringVar(&escape, "escape", "", "set the escape string. if set, a '$' preceded by the escape string does not lead to expansion")
 	flag.Var(&unknownKey, "unknown", "handling of unknown keys, one of [ignore empty error] (default ignore)")
 	flag.Parse()
 	if quiet {
@@ -85,7 +89,8 @@ func main() {
 	s.Split(bufio.ScanLines)
 	for s.Scan() {
 		line := s.Text()
-		_, err := os.Stdout.WriteString(os.Expand(line, subst))
+		line = expand(line, escape, subst)
+		_, err := os.Stdout.WriteString(line)
 		if err != nil {
 			log.Println(err)
 		}