HI Mirod
actually $tag_name=href
$tag_att=attr
$att_value=cde
$tag_text="the string which i want to write in place of old one"

Here I want to rewrite in the file --the text of the tag which is href and having attribute as "attr" value is "cde" and I want to relace this tag text with new "tag_text".

there are two href tags in the file but i want to rewrite the text of only href tag which has attr="cde" in the file.

if i m using the original names in the program then it works but when i m taking them as arguments then it's creating problem.