Similar to other solutions but storing each line along with a reference to the relevant word count hash element in an AoA then using grep and map to print only the lines we want. Note that I have to dereference ( ${ $_->[ 1 ] } ) to get at the value in the hash.

$ perl -Mstrict -Mwarnings -E '
open my $inFH, q{<}, \ <<EOD or die $!;
hello 1234 5698 7458
hi 1457 7459 6214
good_day 1458
hi 1258 3658 
good_morning 4758
hi 1453
EOD

my @lines;
my %counts;

while ( <$inFH> )
{
    my $first = ( split )[ 0 ];
    $counts{ $first } ++;
    push @lines, [ $_, \ $counts{ $first } ];
}

print for
   map  { $_->[ 0 ] }
   grep { ${ $_->[ 1 ] } == 1 }
   @lines;'
hello 1234 5698 7458
good_day 1458
good_morning 4758
$

[download]

I hope this is of interest.

Cheers,

JohnGG

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

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