diff --git a/Dockerfile b/Dockerfile
index 2ec3534..39997b7 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -3,6 +3,7 @@ FROM golang:1.6-alpine
 ENV PATH $PATH:/opt/flamegraph
 
 RUN apk --update add git && \
+    apk add perl && \
     curl -OL https://github.com/Masterminds/glide/releases/download/0.10.1/glide-0.10.1-linux-amd64.tar.gz && \
     tar -xzf glide-0.10.1-linux-amd64.tar.gz && \
     mv linux-amd64/glide /usr/bin && \
diff --git a/README.md b/README.md
index d33a974..72e772b 100644
--- a/README.md
+++ b/README.md
@@ -86,9 +86,12 @@ $ go get github.com/uber/go-torch
 
 You can also use go-torch using docker:
 ```
-$ docker run uber/go-torch -h
+$ docker run uber/go-torch -u http://[address-of-host] -p > torch.svg
 ```
 
+Using `-p` will print the SVG to standard out, which can then be redirected
+to a file. This avoids mounting volumes to a container.
+
 ### Install the Go dependencies:
 
 ```