#! perl -slw
use strict;

open ZCAT, '|-', 'zcat *.gz' or die;

my %uniq;

while( <ZCAT> ) {
    my( $varname ) = m[!dataset_([^=]+)=] or next;
    $uniq{ $varname } = 1;
}

close ZCAT;

print "uniq names sorted";
print for sort keys %uniq;