I was using foreach earlier and some one told me that its deprecated and

They are wrong. foreach is not deprecated. "for" and "foreach" are two keywords that mean the same thing to Perl.

I checked that nothing is open .

Aside from that fact that it's impossible for nothing to be open, how did you determine this?

unlink does not

So the file is read-only, or you don't have permissions to delete it, or some process holds a share or delete lock on the file.