If you can live with a map-less solution, this excludes keys without values:

use warnings;
use strict;
use Data::Dumper;
$Data::Dumper::Sortkeys = 1;

my %info;
while (<DATA>) {
    chomp;
    my ($k, $v) = split /=/;
    $info{$k} = $v if length $v;
}
print Dumper(\%info);

__DATA__
a=5
b=6
c=
d=7
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prints:

$VAR1 = {
          'a' => '5',
          'b' => '6',
          'd' => '7'
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This keeps the key, with a default value:

while (<DATA>) {
    chomp;
    my ($k, $v) = split /=/;
    $info{$k} = (length $v) ? $v : 666;
}
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