temporary_security_group_source_cidrs passing Variable issue

Having three different outcomes which would be expected to drive the same outcome:
1. Hardcoding temporary_security_group_source_cidrs
2. Using a variable-- packer validate .
3. Using a variable-- packer build

When hard coding the CIDR, this works.

However, one would want to tie this to an environmental variable (type string). When doing this, you would validate this: `packer build .` This passes.

However, on the same file, `packer build ' will fail on the same file, throwing an error:
"Error parsing CIDR in temporary_security_group_source_cidrs: invalid CIDR address: "72.X.Y.Z/32"

What is weird is, if you copy and paste this string (72.X.Y.Z/32) this works; both `packer build .` and `packer build ` work as expected.