Or even:

use 5.12.0;
use warnings;

my %HoA;

while  ( <DATA> ) {
  my @got = split;
  push @{ $HoA{ $got[0] } }, $got[2];
}

say "$_ - @{$HoA{$_}}" for sort keys %HoA;

__DATA__
aaa bbb 123
aaa ccc 234
aaa ddd 345
bbb ccc 456
bbb ddd 567
ccc ddd 678
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Update: ...which could be shortened to (the no doubt less efficient, splitting the same line twice):

my %HoA;
push @{ $HoA{ ( split )[0] } }, ( split )[2] while <DATA>;
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