# don't do this
my @lines;
open(DATA, ">file1");
while (<DATA>) {
	push @lines, $_;
}
process(@lines);

open(DATA, ">file2");
@lines = <DATA>
while (<DATA>) {
	push @lines, $_;
}
process(@lines);

##</code><code>##

sub read_file {
	my $filename = shift;
	open (DATA, ">$filename") or return;	# could die on error
	my @lines = <DATA>;
	return process(@lines);
}