#!/usr/bin/perl -w use strict; my @IDS; while () { my @sections = split("\t", $_); my $id = $sections[0]; push @IDS, $id; } my $length = scalar(@IDS); foreach (@IDS) { for (my $i = 0; $i < $length; $i++) { if ($IDS[$i] =~ m/^\s+/) { $IDS[$i] = $IDS[$i-1]; } } } # print scalar(@IDS); print @IDS; __END__