#!/usr/bin/perl
use strict;
use warnings;
# 794700

while(<DATA>){
        # if($_ =~ m/\bpublication date\b/){
	if($_ =~ m/\bpublication date\s/){
	print $_;
	}
}


__DATA__
These are the dates.
The publication date is 20-10-09
The publicatiion dateee is 20-05-08
The publication dat is 10-06-07
The publication date's are 20-10-09,29-02-08

##</code><code>##

perl 794700.pl
The publication date is 20-10-09
The publication date's are 20-10-09,29-02-08

##</code><code>##

perl 794700.pl
The publication date is 20-10-09

##</code><code>##

The publication date is 20-10-09
The publication dates are 20-10-09, 29-02-08)