Try this
#!/usr/local/bin/perl
open (INFILE1, "/home/ashokpj/merge1.txt") ||
die ("Cannot open input file merge1\n");
open (INFILE2, "/home/ashokpj/merge2.txt") ||
die ("Cannot open input file merge2\n");
open (INFILE3, "/home/ashokpj/merge3.txt") ||
die ("Cannot open input file merge2\n");
chomp($line1 = <INFILE1>);
chomp($line2 = <INFILE2>);
chomp($line3 = <INFILE3>);
while ($line1 ne "" || $line2 ne "" || $line3 ne "" ) {
print $line1.$line2.$line3."\n";
if ($line1 ne "") {
chomp($line1 = <INFILE1>);
}
if ($line2 ne "") {
chomp($line2 = <INFILE2>);
}
if ($line3 ne "") {
chomp($line3 = <INFILE3>);
}
}
close(INFILE1);
close(INFILE2);
close(INFILE3);