in reply to blocks and using braces around filehandles with print

print $fh LIST;
and
print { $fh } LIST;
are equivalent.

The curlies are required when dealing with more complex expressions for the file handle. 

>perl -e"my @h = ( \*STDOUT ); print $h[$_] qq{foo!\n} for 0..$#h"
syntax error at -e line 1, near "] qq{foo!\n}"
Execution of -e aborted due to compilation errors.

>perl -e"my @h = ( \*STDOUT ); print { $h[$_] } qq{foo!\n} for 0..$#h"
foo!

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Re^2: blocks and using braces around filehandles with print
by nefigah (Monk) on Mar 16, 2008 at 05:16 UTC

    (Not my question, but thought I'd jump in:)

    So the rules here are the same as whether or not you need curlies for dereferencing an array (etc.)? e.g. @$arrayref but @{ $arrayrefs[0] } ?

    I'm a peripheral visionary... I can see into the future, but just way off to the side.

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      There really isn't any connection between those two kinds of curlies. Those of which you speak act like parens to modify precedence and are solely used in dereferencing. 
      $$array[0]      # Short for ${ $array }[0]
${ $array }[0]  # The first element of the array referenced by $array
${ $array[0] }  # The scalar referenced by the first element of @array

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      A third, similar type of curlies is used in interpolation to show where the variable name ends. 

      "foo$varbar"     # Equivalent to "foo" . $varbar
"foo${var}bar"   # Equivalent to "foo" . $var . "bar"

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        Ah, okay. Thank you :)

        Sorry for the slight hijack!

        I'm a peripheral visionary... I can see into the future, but just way off to the side.

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Re^2: blocks and using braces around filehandles with print
by bramble (Beadle) on Mar 16, 2008 at 17:50 UTC
    The curlies are required when dealing with more complex expressions for the file handle.

    Right, but what I want to know is: what exactly does that thing with the curlies around it evaluate to? I think the problem is, I don't really understand what a BLOCK is.

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      A block is 'code' in this case code that returns a file handle - see how perl deparse's the above code and puts a semicolon before the right curly brace in the code below:
      $ perl -MO=Deparse fh.pl 
      die "Ouch. $!" unless open my $fh, '>', 'foo.txt';
print {$fh;} "hi!\n";
close $fh;

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      fh.pl syntax OK
      (there are probably other methods that you can use to have perl show you what it is "thinking")
      perldoc -f print does mention the blocks 
      Note that if you're storing FILEHANDLEs in an array,
or if you're using any other expression more complex
than a scalar variable to retrieve it, you will have
to use a block returning the filehandle value
instead:

    print { $files[$i] } "stuff\n";
    print { $OK ? STDOUT : STDERR } "stuff\n";

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      A block contains 0 or more Perl statements. A block evaluates the the last value evaluated within the block.

      Examples: 

      { STDOUT }
  -> STDOUT

{ $hash{$k}[$i] }
  -> $hash{$k}[$i]

{ my $x = func(); uc($x) }
  -> uc($x)

{ if ($cond) { 'FOO' } }
  -> If $cond is false, $cond.
  -> If $cond is true, 'FOO'.

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        A block contains 0 or more Perl statements. A block evaluates the the last value evaluated within the block.

        If that's the case, then why doesn't the following work?

        #!/usr/bin/env perl

use strict;
use warnings;

my $foo =
{
    print "hi!\n";
    my $bar = 7;
    my $baz = 8;
};

print "So, \$foo = $foo\n";

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