You're slurping the padding into the values.. do you really want to? Also, a few more spaces help make things pleasing to the eye:

my ($num, $title, $author, $flag1, $flag2) =
    unpack "A7 x1 A27 x1 A25 x1 A1 x5 A1", $str;
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Actually I'd probably write a simple subroutine such that I could say

unpack_fields(
    $str,
    \my $num    => 7,
    padding     => 1,
    \my $title  => 27,
    padding     => 1,
    \my $author => 25,
    padding     => 1,
    \my $flag1  => 1,
    padding     => 5,
    \my $flag2  => 1,
);
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This also clearly documents the data format.

Update: see Yet another unpack wrapper: flatfile databases with fixed width fields.