The snippet 

open FILE, 'test_file.txt' || die "$!\n";
my $text = join( '', @{ [ <FILE> ] } );
close FILE;

[download]
  1. will never die on error,
  2. is inefficient,
  3. uses a global variable (FILE),
  4. would be safer if the 3 parameter open was used, and
  5. will not work on a Windows (and other?) machines without binmode.


It will never die because "||" has higher precedence than ",".

open FILE, 'test_file.txt' || die "$!\n";
means
open FILE, ('test_file.txt' || die "$!\n");
so use
open FILE, 'test_file.txt' or die "$!\n";
or
open(FILE, 'test_file.txt') || die "$!\n";


It is ineffecient you create an anonymous array and immediately dereference it.

join( '', @{ [ <FILE> ] } );
is equivalent to
join( '', <FILE> );

It is also ineffecient because join is slower and less memory efficient than undefining $/.

my $text = join( '', <FILE> );
is equivalent to the more efficient
my $text; { local $/; $text = <FILE>; }


So you end up with 

my $text;
{
   open(my $fh, '<', 'test_file.txt')
      or die("Unable to open input file: $!\n");
   binmode($fh);
   local $/;
   $text = <$fh>;
}

[download]

In reply to Re^2: Determine whether file is dos or unix format by ikegami
in thread Determine whether file is dos or unix format by fritzvtb

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