What you should be doing for a large equi-join like this is a method called "merge-join". The concept is: sort both files first, on the columns you wish to join by, then open up each file, and advance together between the two files. Think of a zipper.

Here's some rough code based on yours (bear in mind that I'm not being super-perfect with this, particularly the initial sort... I'm trying to demonstrate an algorithm):

# assuming this is *nix, or something with a sort utility, otherwise t
+his can be
# done directly in perl
system("sort holds > tmpholds") and die;
system("sort copies > tmpcopies") and die;

open(HOLDS,"<tmpholds") or die;
my (@holds, $holdseof);
sub readhold { ($_=<HOLDS>) || $holdseof++; chomp; @holds = split(/\|/
+,$_,-1); }
readhold;

open(COPIES,"<tmpcopies") or die;
my (@copies, $copieseof);
sub readcopy { ($_=<COPIES>) || $copieseof++; chomp; @copies = split(/
+\|/,$_,-1); }
readcopy;

while(!($holdseof && $copieseof)) {
    if ($holdseof || (!$copieseof && $holds[0] gt $copies[0])) {
        print "copy ($copies[0])\n";
        readcopy;
    }
    elsif ($copieseof || $copies[0] gt $holds[0]) {
        print "hold ($holds[0])\n";
        readhold;
    }
    else {
        print "hold and copy ($holds[0])\n";
        readhold;
        readcopy;
    }
}
close HOLDS;
close COPIES;

__END__

holds
------
iiiii
asdf
fdd
dsafe
dsaf
bfer
rewtewt
bfret
zzzzzzzzz

copies
------
weewr
dddddd
rewtewt
bfret
fdfdsfsdfdsa
dsafe
dsaf
asdf
fdd
bfer

output
------
hold and copy (asdf)
hold and copy (bfer)
hold and copy (bfret)
copy (dddddd)
hold and copy (dsaf)
hold and copy (dsafe)
hold and copy (fdd)
copy (fdfdsfsdfdsa)
hold (iiiii)
hold and copy (rewtewt)
copy (weewr)
hold (zzzzzzzzz)
[download]

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:Wq
Not an editor command: Wq
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