sub foo {
   open FILE, "file.txt";
   bar();
   close FILE;
}
sub bar {
   my @lines = <FILE>;
   # do something here
}

##</code><code>##

sub foo {
   open my $file, "file.txt";
   bar($file);
   close $file;
}
sub bar {
   my ($file) = @_;
   my @lines = <$file>;
   # do something here
}