use strict;

my %data = ();
while (<DATA>) {
    chomp;
    my ($col1, $col2) = split /\s+/;
    $data{$col1} .= "$col2 ";
}

print "$_: $data{$_}\n" foreach (sort keys %data);

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