find word and add words in text file

Wito

Hi, is there any body can help me on this.
i would like to search word in one file (from other file) and if found will be locate in that file, if not will be add to new file.

#!/usr/bin/perl

#Open MPLSIPLIST file
open (MYFILE, "mplsiplist.txt");
$file = ;

#Open ADD/Update file
open (MYADD, "ADD.txt");


open (FILEOUT,">doubleadd.txt");


while ($file) {
$ADDED = ;
#looping
if ($ADDED !~ /^#/) {
chomp ($ADDED);

#find duplicate word
$found = ( $file =~ /(w+)s+$ADDED/gi ) [0];

#Print same word
print FILEOUT "$ADDED!
";
}else{
#Print to mplsiplist file
print MYFILE "$ADDED!
";
}
}

Please help