Create a lookup table from file 2 with the keys being the part of the line excluding the last column. Then go through file 1 and check if the entry is in the lookup table: 

open my $fh1, '<', 'file1.txt' or die $!;
open my $fh2, '<', 'file2.txt' or die $!;
open my $outfh, '>', "outputfile.txt" or die $!;

my %lines;
while (<$fh2>) {
    chomp;
    my ($key, $n) = /(.*)\s(\d+)$/;
    $lines{$key} = $n;
}

while (<$fh1>) {
    chomp;
    if (exists $lines{$_}) {
        print $outfh "$_ $lines{$_}\n";
    } else {
        print $outfh "$_ 0\n";
    }
}

[download]

(this assumes your lookup keys are unique — in case the same key can occur multiple times in file 2, you'd have to think about which entry you then want to have in the output file...)

In reply to Re: comparing 2 files by Eliya
in thread comparing 2 files by garyboyd

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