use strict;
use warnings;
use 5.010;

open my $INFILE, '<', 'data1.txt'
    or die "Couldn't open file: $!";


my %hash;

while (<$INFILE>) {
    chomp;

    my ($first_col, $second_col) = split;
    push @{$hash{$first_col}}, $second_col;
}

while ( my($first_col, $aref) = each %hash ) {
    say "$first_col: ", join(', ', @$aref);
}

close $INFILE;

--output:--
three: goodbye
one: hello, banana
two: world, apple