Geez! What a lot of non-answers for a simple question.

#! perl -slw
use strict;
use Data::Dump qw[ pp ];

my @data = (
    {"name"=>"joe","age"=>21,"weight"=>150,"height"=>"","sex"=>""},
    {"name"=>"joe","age"=>"","weight"=>"","height"=>"6'0","sex"=>""},
    {"name"=>"joe","age"=>"21","weight"=>"","height"=>"","sex"=>"male"
+},
);

my %full;

for my $p ( @data ) {
    $full{ $_ } ||= $p->{ $_ } for keys %$p;
}

pp \%full;

__END__
c:\test>junk17
{ age => 21, height => "6'0", name => "joe", sex => "male", weight => 
+150 }
[download]