Just a general hint: I think it's a good idea to print the reason ($!) when the opening (or else) of a file fails.

Because it gives the user a hint, whats going wrong.

Also it's helpful to name the file...

If you use q(...) or '...', you don't need to double the backslash.

All three tipps together remain in something like

my $file = 'C:\StudyPerl\Projects\tab_file.txt';
open(DAT, $file) or die "Could not open the file '$file': $!";
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hth