Which O'reilley book?

I suggest you start with perlintro, and perlopentut, but basically

open my($fh), '>', '/f/o/o' or die "Can't clobber /f/o/o : $!";
print $fh "stuff\n";
...
[download]

or the slick version

use autodie;
open my($fh), '>' '/f/o/o';
print $fh "stuff\n";
...
[download]