The deref op '->' is unnecessary there, and there is an alternative of nearly the same length with the and op, exists $bar{'foo'} and $bar{'foo'}();

Actually, it wasn't all *that* long ago when the -> wasn't optional in that construct (I believe 5.006 is when that happened and perldelta agrees with me).

It is getting close to long enough ago that I'd forget this fact -- except that I tend to answer a lot of questions from people about Perl and many of those people have surprisingly old versions of Perl. (:

                - tye

I wouldn't actually write that though. I'd write it the way you originally stated: expr->() if expr.

How about this Perl6-ish way:

given %foo{bar} { .() if exists }
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It's still about as much typing, though.

kelan

---

Perl6 Grammar Student

#!/usr/bin/perl -w

use strict;

use vars qw(%bar);

$bar{foo} = sub { print "hello\n"};

callif($bar{foo});
callif($bar{quux});


sub callif
{
  my $var = shift;
  $var->(@_)
      if($var);
}
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# define your hash entry
$foo{bar} = sub { print "Hello Perl!\n" };

# note the use of && operator, which will short-circuit
# if $foo{bar} is undef.
$foo{bar} && $foo{bar}();
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for($bar{foo}) {
    $_->() if $_;
}
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package Tie::HashDefaultValue;
require Tie::Hash;
@ISA = 'Tie::ExtraHash';
use strict;

sub TIEHASH {
  my ($class, $default) = @_;
  return bless [{}, $default], $class;
}

sub FETCH {
  my ($tied, $key) = @_;
  if (exists $tied->[0]{$key}) {
    return $tied->[0]{$key};
  }
  else {
    return $tied->[1];
  }
}

1;
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tie my %bar, 'Tie::HashDefaultValue', sub {};
# time passes
$bar{foo}->();
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PS While writing the above I found a documentation mistake in Tie::Hash. Bug report submitted...

UPDATE: Reading the Tie::Hash source more carefully, I saw that the default TIEHASH function does what mine does, and so that is not needed. If you wish to have people complain about Perl punctuation, here is an amusing implementation of FETCH:

sub FETCH { exists $_[0][0]{$_[1]} ? $_[0][0]{$_[1]} : $_[0][1] }
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eval { use strict 'refs'; $bar{foo}->() };
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