#! perl -slw
use strict;

my (%hash,@order);
while(<DATA>) {
	chomp;
	my @bits = split /\t/;
	push @order, $bits[0] unless exists $hash{$bits[0]};
	$hash{$bits[0]} .= ' ' . $bits[1];
}
print "$_\t$hash{$_}" for @order;

__DATA__
text1	text-a
text2	text-b
text3	text-c
text1	text-d
text3	text-e
text3	text-f