I assume that you mean you want to pull out a specified data set, which is surrounded by { }. If this is correct, how is your data set specified (i.e. by contents, or the name) and what kind of output would you like?
For example, the following works:

#!perl

use strict;
use warnings;

my $lookFor = quotemeta('10.2.56.75');

my $data;
{
   local $/;
   $data = <DATA>;
}

if ($data =~ /lease\s+$lookFor\s+\{([^}]*)\}/) {
   print $1;
} else {
   print "No match\n";
}
__DATA__
lease 10.2.56.40 {
        starts 3 2003/08/20 10:37:28;
        ends 3 2003/08/20 22:37:28;
        hardware ethernet 00:20:af:52:12:0f;
        uid 01:20:af:52:12:0f;
        client-hostname "Telephone";
}
lease 10.2.56.75 {
        starts 3 2003/08/20 09:57:11;
        ends 3 2003/08/20 21:57:11;
        hardware ethernet 00:ef:18:ae:52:83;
        uid 01:00:ef:18:ae:52:83;
        client-hostname "beast";
}
lease 10.2.56.77 {
        starts 2 2003/08/19 21:13:05;
        ends 3 2003/08/20 21:13:05;
        hardware ethernet 00:02:95:9b:78:18;
        uid 01:02:0b:95:9b:78:18;
}
[download]

producing the output

        starts 3 2003/08/20 09:57:11;
        ends 3 2003/08/20 21:57:11;
        hardware ethernet 00:ef:18:ae:52:83;
        uid 01:00:ef:18:ae:52:83;
        client-hostname "beast";
[download]

but unless you provide more specific information, it will be hard (at least for me) to answer this question.