How to Execute bash code in EC2 instance from Automation Document deployed with CloudFormation

I'm trying to execute bash code via aws:runcommand. I have taken and adapted the below snippet from the AWS Repo to deploy a Golden Image pipeline

What you see below is deployed via a CloudFormation Stack. An AWS::SSM::Document object is formed, passing various inputs. This is one of the mainSteps of my automation document. I'm trying to update the OS of my instance.

{

   "name": "updateOSSoftware",

   "action": "aws:runCommand",

   "maxAttempts": 3,

   "timeoutSeconds": 3600,

   "onFailure": "Abort",

   "inputs": {

       "DocumentName": "AWS-RunShellScript",

       "InstanceIds": [

           "{{startInstances.InstanceIds}}"

       ],

       "Parameters": {

           "commands": [

               "export https_proxy=http://myproxy.com:myport",

                "export https_proxy='{{OutBoundProxy}}'",

                "set -e",

               "[ -x \"$(which wget)\" ] && get_contents='wget $1 -O -'",

               "[ -x \"$(which curl)\" ] && get_contents='curl -s -f $1'",

               "eval $get_contents https://aws-ssm-downloads-eu-west-1.s3.amazonaws.com/scripts/aws-update-linux-instance > /tmp/aws-update-linux-instance",

               "chmod +x /tmp/aws-update-linux-instance",

               "/tmp/aws-update-linux-instance --pre-update-script '{{PreUpdateScript}}' --post-update-script '{{PostUpdateScript}}' --include-packages '{{IncludePackages}}' --exclude-packages '{{ExcludePackages}}' 2>&1 | tee /tmp/aws-update-linux-instance.log"

           ]

       }

   }

}

Once I execute the document from the Systems Manger, I SSH into the EC2 instance and trying and echo $http_proxy, the variable is unset, showing the code wasn't launched.

How can I run bash code?