&ellip;and if toolic's suggestion won't always work, i.e., the number of columns changes, you could try something like this:

#/usr/bin/perl

use strict;
use warnings;

while(<DATA>){
    (my $junk, my $keep) = split(/\s1000\s/, $line, 2);
    my @datum = split(/\s+/,$keep);
    print shift(@datum),"\n";
}
__DATA__
*> 4.23.88.0/23     64.135.0.1                             0 1000 234 
+46164 i
*> 4.23.89.0/24     64.135.0.1                             0 1000 2014
+8 46164 i
*> 4.23.92.0/23     64.135.0.1                             0 1000 2013
+8 46164 i
*> 4.23.92.0/22     64.135.0.1                             0 1000 3018
+ 46164 i
*> 4.23.94.0/23     64.135.0.1                             0 1000 4041
+8 46164 i
*> 4.23.112.0/24    64.135.0.1                             0 1000 1018
+ 174 21889 i
*> 4.23.113.0/24    64.135.0.1                             0 1000 2018
+ 174 21889 i
*> 4.23.114.0/24    64.135.0.1                             0 1000 18 1
+74 21889 i
*> 4.36.118.0/24    64.135.0.1                             0 1000 7018
+ 174 21889 i
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