REGEXP_LIKE in pl/sql block

hi gays

have a nice day

i need some help with pl/sql coding

i have this working code

select str from (SELECT '4893471234566835' as str  FROM DUAL) where REGEXP_LIKE(str, '[[:digit:]]{16}');

select str from (SELECT '4893471234566835' as str  FROM DUAL) where REGEXP_LIKE(str, '\d{16}');

and i need to transform it with 'ESC' in pl/sql block, but i cant do it right

EXECUTE IMMEDIATE

--'SELECT str FROM (select "'||tn_cn.owner||'"."'||tn_cn.table_name||'"."'||tn_cn.column_name||'" as str from "'||tn_cn.owner||'"."'||tn_cn.table_name||'") where  rownum <=1' BULK COLLECT INTO pan_array;  --works fine