I just tried a code but it won't work...When I run it loop doesn't end and need the output. could anybody shortout this

Well, you're matching against $xmlin in a loop, and then you try to do substitutions against $xmlin inside that loop -- this is not going to work

This is the loop you want  $xmlin =~ s/(<([^>]*)>)/ReplaceOrNot("$1")/sgie;

See perlfaq6, perlrequick for more examples

perlfaq6/How can I hope to use regular expressions without creating illegible and unmaintainable code?

perlfaq6/How do I efficiently match many regular expressions at once?

perlfaq6/What good is \G in a regular expression?