use strict;
use warnings;

my $flag = 0;
my @lines;
while (<DATA>) {
    if (/SUBSCRIBER/ .. /NATIONAL/) {
        push @lines, $_;
        $flag = 1 if /A1/;
        if (/NATIONAL/) {
            print @lines if $flag; 
            $flag = 0;
            @lines = ();
        }
    }
}