What is the best way to slurp a file into a string in Perl?

Question

How about this:

use File::Slurp;
my $text = read_file($filename);

ETA: note Bug #83126 for File-Slurp: Security hole with encoding(UTF-8). I now recommend using File::Slurper (disclaimer: I wrote it), also because it has better defaults around encodings:

use File::Slurper 'read_text';
my $text = read_text($filename);

or Path::Tiny:

use Path::Tiny;
path($filename)->slurp_utf8;

I like doing this with a do block in which I localize @ARGV so I can use the diamond operator to do the file magic for me.

 my $contents = do { local(@ARGV, $/) = $file; <> };

If you need this to be a bit more robust, you can easily turn this into a subroutine.

If you need something really robust that handles all sorts of special cases, use File::Slurp. Even if you aren't going to use it, take a look at the source to see all the wacky situations it has to handle. File::Slurp has a big security problem that doesn't look to have a solution. Part of this is its failure to properly handle encodings. Even my quick answer has that problem. If you need to handle the encoding (maybe because you don't make everything UTF-8 by default), this expands to:

my $contents = do {
    open my $fh, '<:encoding(UTF-8)', $file or die '...';
    local $/;
    <$fh>;
    };

If you don't need to change the file, you might be able to use File::Map.

In writing File::Slurp (which is the best way), Uri Guttman did a lot of research in the many ways of slurping and which is most efficient. He wrote down his findings here and incorporated them info File::Slurp.

open(my $f, '<', $filename) or die "OPENING $filename: $!\n";
$string = do { local($/); <$f> };
close($f);