Use [is[current]fields[]] to generate the list of fields in the current tiddler.
Then "get" the value of each fieldname and test it has a prefix and suffix of xyz
Tony
\define find-in-fields(tid value)
<$list filter="[[$tid$]fields[]] -text" variable="thefield">
<<findvalue tid:"$tid$" value:"$value$">>
</$list>
\end
\define findvalue(tid value)
<$list filter="[[$tid$]field:$(thefield)$[$value$]]">
$(thefield)$ : $value$
</$list>
\end
<<find-in-fields tid:"My Tiddler" value:XYZ>>