my $fh;

if (! open $fh, '<', $file){
    die $!;
}

# you can successfully use fh here...
# it'll only close if you "close $fh or die $!;", or when the file (program) exits

# the above example has the same effect of doing the below example, but this is 
# easier as you don't have a bunch of variables declared at the top of your file.

# the entire idea is to keep variables declared, defined as close to
# the place you intend to use them

open my $fh, '<', $file or die $!;