I am playing with List::MoreUtils::pairwise and noticed some funny
behaviour. I'm trying to merge two lists of hashes into one list of
hashes:
p...@tui:~/tmp$ cat bar.pl
use strict;
use warnings;
use List::MoreUtils qw(pairwise);
use Data::Dumper;
my @aoh_a = ( { foo => 1, bar => 2 }, {foo => 3, bar => 4} );
my @aoh_b = ( { fred => 5, jim => 23}, {fred => 1089, jim => 1729} );
my @aoh = pairwise { return { %{$a}, %{$b} } } @aoh_a, @aoh_b;
print Dumper(\...@aoh);
p...@tui:~/tmp$ perl bar.pl
Name "main::b" used only once: possible typo at bar.pl line 10.
Name "main::a" used only once: possible typo at bar.pl line 10.
$VAR1 = [
{
'bar' => 2,
'jim' => 23,
'foo' => 1,
'fred' => 5
},
{
'bar' => 4,
'jim' => 1729,
'foo' => 3,
'fred' => 1089
}
];
This works fine. But I noticed that if I remove the explicit "return"
in the pairwise block, I get different results:
p...@tui:~/tmp$ cat bar.pl
use strict;
use warnings;
use List::MoreUtils qw(pairwise);
use Data::Dumper;
my @aoh_a = ( { foo => 1, bar => 2 }, {foo => 3, bar => 4} );
my @aoh_b = ( { fred => 5, jim => 23}, {fred => 1089, jim => 1729} );
my @aoh = pairwise { { %{$a}, %{$b} } } @aoh_a, @aoh_b;
print Dumper(\...@aoh);
p...@tui:~/tmp$ perl bar.pl
Name "main::b" used only once: possible typo at bar.pl line 10.
Name "main::a" used only once: possible typo at bar.pl line 10.
$VAR1 = [
'bar',
2,
'foo',
1,
'jim',
23,
'fred',
5,
'bar',
4,
'foo',
3,
'jim',
1729,
'fred',
1089
];
Is this because the curlies are being interpreted as a block rather
than an anonymous hash constructor? If so, when are they anonymous
hash constructors and when are they blocks? How might I avoid this
issue in future? And secondary question: how can I avoid the warnings
about $main::a and $main::b?
Philip
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