I noticed that some shells like ye olde bash available on SmartOS don't
treat the following construct as single a token:

    ${dir}/${file}

The following expands a single token on the RHS even if the variable
contains spaces:

    var=${dir}

But a token involving a regular string too needs to be protected by
double quotes:

    var="${dir}/${file}"

Even when none of the variables contain blanks.

Refs #2139