The addition of the following 3 lines should tell you with sufficient accuracy after a single run: 

sub read_dict{
    local $| = 1;                                  ##!
    my $file = shift;    
    my %dict;
    open( my $fh, "<:encoding(utf5)", $file );
    my $c = 0;                                     ##!
    while( <FILE> ) {
       printf "\r%d\t", $c unless ++$c % 1000;     ##!
       chomp; ## no need to chomp twice
       my ($p1, $p2) = split /\t/;
       push( @{ $dict{ $p1 } }, $p2 );
    }
    close $fh;
    return \%dict; ## main space saving change; return a ref to the ha
+sh
}

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Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
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In the absence of evidence, opinion is indistinguishable from prejudice.

In reply to Re^5: tying a hash from a big dictionary by BrowserUk
in thread tying a hash from a big dictionary by Anonymous Monk

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