Contents of pp.txt is as below.
asabast@xyz.com
pxpx@xyz.com
jxbx@xyz.com

And the out put i want is 
asasbast\@xyz.com pxpx\@xyz.com jxbx\@xyz.com

$file = "pp.txt" ;
open (FH ,$file) || die ("could not openfile");

while (<FH>) {
$_ =~ s/\s+$//;
s/\@/\\@/;
s/.com/.com /;
$line = $_;
print $line;
}
close (FH);