tidbit for today: if you would like to prefix (or suffix) some field with text, but only if it has content, normally you'd write something like:

<#if record.field?has_content>prefix: ${record.field}</#if>

or

${record.field?has_content?then('prefix: '+record.field,'')}

you can leverage the string built-in ?ensure_starts_with/?ensure_ends_with with a regexp pattern instead:

${record.field?ensure_starts_with('^$','prefix: ')