Good god, man! Think a little bit. This is a standard ETL action.

my %passwd;
my %smbpasswd;

while (<PASSWD>)
{
    next if /^#/;
    chomp;
    my ($name, $uid) = (split ':', $_, 4)[0,2];
    $passwd{$uid} = $name;
}

# Do the same for SMBPASSWD, except use [0,1] instead of [0,2]

foreach my $uid (keys %passwd)
{
    unless (exists $smbpasswd($uid})
    {
        print "'$uid' in passwd, not in smbpasswd\n";
        next;
    }

    # Deleted to do later comparison
    my $smb_name = delete $smbpasswd{$uid};

    unless ($passwd{$uid} eq $smb_name)
    {
        print "$uid has $passwd{$uid} in passwd, but $smb_name in smbb
+passwd\n";
    }
}

while (my ($k, $v) = each %smbpasswd)
{
    print "$k in smbpasswd, not in passwd\n";
}
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