in reply to Merge two huge datasets by ID

my ($File_1_line,$File_2_line); open(F1,"File_1"); open(F2,"File_2"); while($File_1_line=<F1>) { #chomp $File_1_line; my @data=split(' ',$File_1_line); seek(F2,0,0); while($File_2_line=<F2>) { chomp $File_2_line; print "@data\n" if($data[0] eq $File_2_line); } }

Try this it will help you.