@vuk when setting a variable to a string as in your example you can use define, procedure pragma but also $set, $vars and the best $let
\procedure tiddler-title() [[JeremyRuston]]
and use `<tiddler-title>` in your filters
or
<$let tiddler-title="[[JeremyRuston]]">
and use `<tiddler-title>` in your filters
</$let>
However;
There are otherways to populate fields, lists and handle titles that handle the use of [[name with spaces]] namewithoutspaces including but not limited to the listops action widget.