But that puts the whole file into the first element of the array. (Change your print to print "|$_|\n" for @fin; and you'll see only one element.)
You probably want this:
$/ = undef;
open "FIN", "<raja.txt" or die "cant open :$!";
my @fin = split/\n/,<FIN>;
close FIN;
print "|$_|\n" for @fin;
Or to also get rid of blank lines:
...
my @fin = grep {$_} split /\n/, <FIN>;
Update: Square brackets in my original post created a link I didn't intend. I changed them to pipes. And alternatively, you could just print scalar @fin to confirm how many items you slurped.