Hi choroba, Thank you for helping out and for your explanation. I use $#data ++ because I just followed some example I found. Is this how I supposed to write again? 
#! /usr/bin/perl

my $file = 'input';
open my $fh, '<', $file or die "cant open : $!";
@data=<$fh>;
while (my $line = <>) {
    if ($line =~ /^(.*) (\d+)$/) {
            push @data, $1;
     }
}

for my $d (@data) {
       print "$d\n";
}

close $fh;

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It doesn't work though. Do you mind show me a detailed code that I could possibly implement? Thank you!

In reply to Re^2: using while, first line was skipped by rendus
in thread using while, first line was skipped by rendus

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