Thank you for a tip.

Searching for uids less than 1000 and gt 500... Net::LDAP=HASH(0x22d4e
+e0) sending:
0000   82: SEQUENCE {
0002    1:   INTEGER = 2
0005   77:   [APPLICATION 3] {
0007   39:     STRING = 'ou=slurm,dc=lomonosov,dc=parallel,dc=ru'
0030    1:     ENUM = 2
0033    1:     ENUM = 2
0036    1:     INTEGER = 0
0039    1:     INTEGER = 0
003C    1:     BOOLEAN = FALSE
003F   17:     [CONTEXT 6] {
0041    9:       STRING = 'uidNumber'
004C    4:       STRING = '1000'
0052     :     }
0052    0:     SEQUENCE {
0054     :     }
0054     :   }
0054     : }
Net::LDAP=HASH(0x22d4ee0) received:
0000   12: SEQUENCE {
0002    1:   INTEGER = 2
0005    7:   [APPLICATION 5] {
0007    1:     ENUM = 0
000A    0:     STRING = ''
000C    0:     STRING = ''
000E     :   }
000E     : }
Ok
Found:
[download]

I suppose that 'context 6' in this context means 'less or equal'; according to rfc,

        LDAPMessage ::= SEQUENCE {
             messageID       MessageID,
             protocolOp      CHOICE {
                  bindRequest           BindRequest,
                  bindResponse          BindResponse,
                  unbindRequest         UnbindRequest,
                  searchRequest         SearchRequest,
                  searchResEntry        SearchResultEntry,
                  searchResDone         SearchResultDone,
[...]
        SearchRequest ::= [APPLICATION 3] SEQUENCE {
             baseObject      LDAPDN,
             scope           ENUMERATED {
                  baseObject              (0),
                  singleLevel             (1),
                  wholeSubtree            (2),
                  ...  },
             derefAliases    ENUMERATED {
                  neverDerefAliases       (0),
                  derefInSearching        (1),
                  derefFindingBaseObj     (2),
                  derefAlways             (3) },
             sizeLimit       INTEGER (0 ..  maxInt),
             timeLimit       INTEGER (0 ..  maxInt),
             typesOnly       BOOLEAN,
             filter          Filter,
             attributes      AttributeSelection }
[...]
        Filter ::= CHOICE {
[...]
             greaterOrEqual  [5] AttributeValueAssertion,
             lessOrEqual     [6] AttributeValueAssertion,
[...]
        AttributeValueAssertion ::= SEQUENCE {
             attributeDesc   AttributeDescription,
             assertionValue  AssertionValue }

        AttributeDescription ::= LDAPString
                                -- Constrained to <attributedescriptio
+n>
                                -- [RFC4512]

        AssertionValue ::= OCTET STRING
[download]

Everything seems to be OK, but *why* console utility 'ldapsearch' returns ~200 entries, and Net::LDAP doesn't?