How about this approach: 
my @array = (
"hello 1234 5698 7458",
"hi 1457 7459 6214",
"good_day 1458",
"hi 1258 3658",
"good_morning 4758",
"hi 1453",
);

# count all occurences
my %freqs;
for my $elem (@array) {
    my ($word) = $elem =~ /^(\w+)/;
    $freqs{$word}++;
}

# remove all multifrequent words
my @new_array;
for my $elem (@array) {
    my ($word) = $elem =~ /^(\w+)/;
    unless ($freqs{$word} > 1) {
        push @new_array, $elem;
    }
}

[download]
edit: corrected - element needs to be removed

In reply to Re: Removing certain lines from array by arkturuz
in thread Removing certain lines from array by Dr Manhattan

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