#!/usr/bin/env perl

use strict;
use warnings;

open(my $infh, '<', 'testdat.dat') or die $!;

my $outfh;
my $filecount = 0;
while ( my $line = <$infh> ) {
    if ( $line =~ /^zone>\s*(\w+\W+(\w+)\s*$)/ ) {
        close($outfh) if $outfh;
        $outfh = $2;
        open($outfh, '>', sprintf($outfh'.txt', ++$filecount)) or die $!;
    }
    print {$outfh} $line or die "Failed to write to file: $!";
}

close($outfh);
close($infh);


Datafile =

zone 1filea  1ss
record1a
record1b
record1c
record	1d	2
record	empty
endoffile

zone 2fileb  1ss
record1a
record1b
record1c
record	1d	2
record	empty
endoffile