I prefer to keep such things as simple as possible unless there is a significant performance advantage. I'd prefer something like:

my $checked = $fieldValues{fieldName} ? 'checked="checked"' : '';
print qq{<input type="checkbox" name="fieldName" value="1" $checked/>\
+n};
[download]

or possibly

printf qq{<input type="checkbox" name="fieldName" value="1" %s/>\n}, $
+fieldValues{fieldName} ? 'checked="checked"' : '';
[download]