Hello, and welcome to the Monastary!

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<UPDATE>:Thank you namisha for updating your post and fixing formatting.
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The examples you posted do not look like XML , and they have unmatched quotes.

You can write a script to verify the "datasize" by learning how to open and read files in perl, in Tutorials.
Learn regular expressions to extract the "datasize".

Here is a sample regular expression to get you started:

my $data = "... domainType="TRWF_TRDM_DMT_MARKET_BY_PRICE dataSize:500
+0";
my ($datasize) = $data=~/dataSize:(\d+)/;
[download]

If your files are proper XML, you can use one of several XML libraries on cpan.

If you get into trouble with coding, please post your attempt, and problem here .. we will be glad to help.