I agree with most of the other posters so far: this is very incomplete (and thus very confusing) code.

I think you want to read a flat file in, use the first word on each line as a key, then assign something as the value in a hash. If so, maybe you're looking for something like this?

my %hash;
while ( <FILE> )
{
    my ( $key ) = ( m/^(\w+)/ )
      or next;
    $hash{$key} = 'whatever';
}
[download]

If you are doing something with the rest of the line, maybe you want to do a limited split on whitespace instead ... ah, no, you want a literal vertical bar:

my %hash;
while ( <FILE> )
{
    my ( $key, $value ) = split /\|/, $_, 2;
    next unless $key;
    $hash{$key} = $value;
}
[download]

If neither of the above are what you're trying to do, consider restating your original question. (For the record, I consider hashes with hundreds of thousands of elements to be "immense" on current machines — a few hundred should be trivial.)

Finally, never ever ever use $1 and friends without first checking for the success of a match. In your code, you do:

/^(\w+)\|/;
$hash{$1)='blah';
[download]

It is entirely possible that the regex might not match, in which case $1 will be undef. Make the assignment conditional:

if ( /^(\w+)\|/ ) { $hash{$1} = 'blah' }
[download]

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