Unlike the other folks who replied above, I tried to extract the seem to be replying to a version of the OP that contains perl code and data that you attempted to include in your post.

First: Please update your post and place "code" tags around your sample data and code snippet, like this:

<code>  <- you need to type in these tags exactly as shown

# xml data:
<gname>abc</gname>   <-- then you can type these exactly as shown.
<pname>xyz</pname>

# html data:
<p>ABC</p>
<p><i>xyz</i></p>

</code>
[download]

and like this:

<code>

open(F2,"<F2>");
my $xml_list1="(.*)\.html";

# here the data enclosed inside the parentheses also appears when
# printed. I want say the file name is "abc.html" so i want to keep
# "abc" as interchangeable, so that i dont need to write/modify the
# code if any filename other than abc.html occurs.

close F2;
#print $xml_list1."\n";

foreach my $f (@filenames)
{
#print $f."\n";
    open(F1,"<F1>");
    my $data=join("",<F1>);
    close F1;
    my $filename=substr($f,0,index($f,'.'));
    my $xml_list=$filename.".xml";

    while($xml_list=~m//ig)

# the code doesn't enter the while/if loop, seems that it finds some
# error in reading the filename $xml_list, but i tried using
# $xml_list1 too... but still the loop doesnt work.

</code>
[download]

Now that your data and snippet are more visible to people, I would say that there's still not enough for us to work with. Your sample data is too sparse, the code incomplete and makes no sense, and you don't give a clear explanation of what you're actually trying to accomplish. What should your script produce as output?

You might want to look at this code I posted a while ago, for using XPath expressions on a command line to extract portions of XML: Re: XPath command line utility... -- it might give you a starting point for extracting "gname/pname" elements from your xml file, and might work on the html data also.