Quick and dirty solution using a state variable: 
use strict;
use warnings;

my $flag = 0;
while (<DATA>) {
    if (/^CHAN_TYPE\s+TCH/) { $flag = 1 }
    if ($flag) {
        if (/Px,Py/) {
            print;
            $flag = 0;
        }
    }
}

__DATA__

[download]
==============================================
CALL_INIT       2008/09/08 15:21:56.958
TRAN_ID         deadbeeffe3
CGI             310-26-1-1
CHAN            N/A
CHAN_MODE       Speech Version 2 (EFR)
CHAN_TYPE       TCH/EFR
SUB_CHAN        0
TIMESLOT        3
TSC             4
HOPPING         Enabled
MAIO            0
HSN             0
MA              528,529,530,531,532,533,534,542,543,544,545
ENCR            N/A
SESSION_KEY     N/A
RESPONSE_TIME   20000 ms
==============================================
CALL_RESPONSE           2008/09/08 15:21:59.223
TRAN_ID                 deadbeeffe3
CGI                     310-26-1-1
PLR_RESPONSE_TIME       20000 ms
Px,Py = bfbc76e04a8768e2,3faca2020f5a215b
UNCERTAINTY MAJOR       0x2 (2 m)
UNCERTAINTY MINOR       0x2 (2 m)
CONFIDENCE              70 %
TYPE OF SHAPE           3
LOCATION METHOD         8
==============================================
==============================================
CALL_INIT       2008/09/08 15:21:56.958
TRAN_ID         deadbeeffe3
CGI             310-26-1-1
CHAN            N/A
CHAN_MODE       Speech Version 2 (EFR)
CHAN_TYPE       FOO
SUB_CHAN        0
TIMESLOT        3
TSC             4
HOPPING         Enabled
MAIO            0
HSN             0
MA              528,529,530,531,532,533,534,542,543,544,545
ENCR            N/A
SESSION_KEY     N/A
RESPONSE_TIME   20000 ms
==============================================
CALL_RESPONSE           2008/09/08 15:21:59.223
TRAN_ID                 deadbeeffe3
CGI                     310-26-1-1
PLR_RESPONSE_TIME       20000 ms
Px,Py = 00000000000000000,00000000000000000000
UNCERTAINTY MAJOR       0x2 (2 m)
UNCERTAINTY MINOR       0x2 (2 m)
CONFIDENCE              70 %
TYPE OF SHAPE           3
LOCATION METHOD         8
==============================================

[download]

prints: 

Px,Py = bfbc76e04a8768e2,3faca2020f5a215b

[download]

In reply to Re: Simple log parser I hope! by toolic
in thread Simple log parser I hope! by picabotwo

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