# always start your scripts with these two lines...
use strict;
use warnings;

# and declare your variables

foreach my $i (2 .. 4) {
    my $filename = 'T' . $i . 'T.txt';
    open (my $file, $filename) or die "Can't open '$filename': $!";
    my @a = <$file>;
    print @a;
    close $file;
}