Since you are in single-quotes, attempting to escape the $ using \$ causes the $ to be interpreted literally by perl where you did not intend.

Specifically, I think you intended perl to see "$var" , but you have a "\" preceding the $ , and that \ is passed to perl, so perl thinks you want a literal $var, instead of interpolating.

Here is how perl currently sees your re:

  s#\Q(.*)\$/',\$lines,\$matches))10.(.*)\$/',\$lines,\$matches))(.*)\
+$/',\$lines,\$matches))# #gi
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Update:The problem is that \Q interpolates and disallows \$ - see my response below.

Hi , yeah I have tried removing all the '\' before the '$' But still the same..No matched pattern stored in result1.txt Thanks,

This one works:

perl -ne 'BEGIN{ $s=q ~(.*)$/'"'"',$lines,$matches)        10.(.*)$/'"
+'"',$lines,$matches)     (.*)$/'"'"',$lines,$matches)~};print unless 
+/\Q$s\E/' input.txt
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Instead of doing an in-place replace , You can redirect the output of this to the final file.

It seems like "\Q" and the "$" symbol do not interact well when directly in a RE.

If you put the "$" symbols outside \Q..\E , it seems to work.

Here is the quote from http://www.perl.com/doc/manual/html/pod/perlre.html

You cannot include a literal $ or @ within a \Q sequence. An unescaped $ or @ interpolates the corresponding variable, while escaping will cause the literal string \$ to be matched. You'll need to write something like m/\Quser\E\@\Qhost/.

So, this one works too ..(But it sure is UGLY!)

 perl -ne 'print unless m~\Q(.*)\E\$/'"'"',\$lines,\$matches\Q)       
+ 10.(.*)\E\$/'"'"',\$lines,\$matches\Q)     (.*)\E\$/'"'"',\$lines,\$
+matches\)~x' input.txt
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