try {
    $tok = Invoke-RestMethod -Method Put `
        -Uri "http://169.254.169.254/latest/api/token" `
        -Headers @{"X-aws-ec2-metadata-token-ttl-seconds"="60"} -TimeoutSec 2
    $region = Invoke-RestMethod `
        -Uri "http://169.254.169.254/latest/meta-data/placement/region" `
        -Headers @{"X-aws-ec2-metadata-token"=$tok} -TimeoutSec 2
    "EC2 in region: $region"
} catch { "Not EC2 - on-prem" }