/^(\S+)/ && print "$1\n" while <DATA>;

__DATA__
EXAMPLE1    NS    ns0.test.com
            NS    ns1.test.com
EXAMPLE2    NS    ns0.test.com
            NS    ns1.test.com
EXAMPLE3    NS    ns0.test.com
            NS    ns1.test.com
EXAMPLE4    NS    ns0.test.com
            NS    ns1.test.com

# this prints
EXAMPLE1
EXAMPLE2
EXAMPLE3
EXAMPLE4

##</code><code>##

while (my $line = <DATA>) {
    if ( $line =~ /^(\S+)/ ) {
        print "$1\n";
    } 
}