You could do it with more error checking.

my $file = 'file.dat';
open my $fh, '>', $file
    or die "Can't write '$file': $!";
close $fh or die "Close error: $!";
[download]

You could do it with a call to the shell. (If 'file.dat' is not really a literal, you have to watch out for shell metacharacters in the filename.)

system( "echo -n > file.dat" );
[download]

Or you could just use truncate:

truncate 'file.dat', 0
    or die "Can't truncate file.dat: $!";
[download]