#!/usr/bin/perl -W
$str = <STDIN>;# suppose $str = "i am perl: a system";
chomp($str);
$query = <STDIN>;# suppose $query = 'perl';
chomp($query);
#$query = "perl";
$str =~ s/$query\W+/<em>$query<\/em> \W+/ig;

print " Value = " . $str;