G'day dwslovedh,

I found your problem description very hard to follow. Do you want something like this?

#!/usr/bin/env perl

use strict;
use warnings;

my $closest;

while (<DATA>) {
    print;

    if (/^MSG_ID_CELL_INFO_PRINT/) {
        $closest = $_;
    }

    if (/^MSG_ID_CELL_CAMP_REQ/) {
        print "\tClosest: $closest";
    }
}

__DATA__
MSG_ID_CELL_INFO_PRINT sn=1 cellid=2; 
MSG_ID_CAMP_RSP sn=2 cellid=2; 
MSG_ID_CELL_INFO_PRINT sn=3 cellid=5;
MSG_ID_CELL_INFO_PRINT sn=5 cellid=2;
MSG_ID_CAMP_RSP sn=6 cellid=4; 
MSG_ID_CAMP_RSP sn=8 cellid=2;  
MSG_ID_CELL_INFO_PRINT sn=10 cellid=2; 
MSG_ID_CELL_INFO_PRINT sn=11 cellid=5; 
MSG_ID_CAMP_RSP sn=12 cellid=2; 
MSG_ID_CAMP_RSP sn=14 cellid=3; 
MSG_ID_CELL_CAMP_REQ sn=15 cellid=2; 
MSG_ID_CELL_INFO_PRINT sn=16 cellid=2; 
MSG_ID_CELL_INFO_PRINT sn=17 cellid=2; 
MSG_ID_CELL_INFO_PRINT sn=18 cellid=2; 
MSG_ID_CAMP_RSP sn=19 cellid=2; 
MSG_ID_CELL_INFO_PRINT sn=20 cellid=5; 
MSG_ID_CELL_INFO_PRINT sn=21 cellid=2;
MSG_ID_CAMP_RSP sn=22 cellid=4; 
MSG_ID_CAMP_RSP sn=23 cellid=2;  
MSG_ID_CELL_INFO_PRINT sn=24 cellid=2;  
MSG_ID_CELL_CAMP_REQ sn=25 cellid=2;
[download]

Output:

$ pm_msg_block_extract.pl
MSG_ID_CELL_INFO_PRINT sn=1 cellid=2; 
MSG_ID_CAMP_RSP sn=2 cellid=2; 
MSG_ID_CELL_INFO_PRINT sn=3 cellid=5;
MSG_ID_CELL_INFO_PRINT sn=5 cellid=2;
MSG_ID_CAMP_RSP sn=6 cellid=4; 
MSG_ID_CAMP_RSP sn=8 cellid=2;  
MSG_ID_CELL_INFO_PRINT sn=10 cellid=2; 
MSG_ID_CELL_INFO_PRINT sn=11 cellid=5; 
MSG_ID_CAMP_RSP sn=12 cellid=2; 
MSG_ID_CAMP_RSP sn=14 cellid=3; 
MSG_ID_CELL_CAMP_REQ sn=15 cellid=2; 
    Closest: MSG_ID_CELL_INFO_PRINT sn=11 cellid=5; 
MSG_ID_CELL_INFO_PRINT sn=16 cellid=2; 
MSG_ID_CELL_INFO_PRINT sn=17 cellid=2; 
MSG_ID_CELL_INFO_PRINT sn=18 cellid=2; 
MSG_ID_CAMP_RSP sn=19 cellid=2; 
MSG_ID_CELL_INFO_PRINT sn=20 cellid=5; 
MSG_ID_CELL_INFO_PRINT sn=21 cellid=2;
MSG_ID_CAMP_RSP sn=22 cellid=4; 
MSG_ID_CAMP_RSP sn=23 cellid=2;  
MSG_ID_CELL_INFO_PRINT sn=24 cellid=2;  
MSG_ID_CELL_CAMP_REQ sn=25 cellid=2; 
    Closest: MSG_ID_CELL_INFO_PRINT sn=24 cellid=2;
[download]