The <sequential> type doesn't support nested text data ("\")

Question

I am executing an ANT target where I write to copy a zip file from 1 folder to another folder. For copying a list of files I have used a "for" loop. While executing this I am facing this issue:

The <sequential> type doesn't support nested text data ("\").

My script in the target is as follows:

<for param="MyZipParameter" list="${FilesInsideZipFile}" delimiter=";">
       <sequential>
          <if>
            <matches string="@{MyZipParameter}" pattern="UpdateSite*" />
              <then>

I am facing the issue during starting of "if" block in the script. I thought some invisible characters might be there and I have removed the script and without copying I have typed the script again, but still same the issue occurs during execution.

This totally blocked my work and I could not find any clue on this. Please help and provide your inputs.