Assuming that the data is in a file called "data.txt", I might try something like the following (untested):

#!/usr/bin/perl -w
use strict;

my %somehash;
my $file = 'data.txt';

open FILE "<$file" or die "Can't open $file for reading: $!";
while (<FILE>) {
    if (/^(\d+)\s+[^\s]+\s+[^\s]+\s+([a-zA-Z]+)$/ {
        $somehash{$2} = $1;
    }
}
[download]

The regex breaks out as follows:

/^            # Anchor to beginning of string
  (           # Capture to $1
    \d+       #     one or more digits
  )           # 
  \s+         # One or more whitespace
  [^\s]+      # One or more non-whitespace
  \s+         # One or more whitespace
  [^\s]+      # One or more non-whitespace
  \s+         # One or more whitespace
  (           # Capture to $2
    [a-zA-Z]+ #     One or more letters
  )           #
$/x;          # Anchor to end of string
[download]

For more information about why I did not use a simpler regex like /^(\d+).*\b(\w+)$/, you may want to read Death to Dot Star!.

Simpler, however, would be to use a split (also untested):

while (<FILE>) {
    chomp;
    my ($value, $key) = (split /\s/, $_)[0,3];
    $somehash{$key}   = $value;
}
[download]

Cheers,
Ovid

Update: I would just like to say that I have no frickin' idea why I wrote that regex. Yes, it works. So what? I saw regex in the title and got carried away.

Use the split;

UpdateII: Yup. I have the key value backwards. It's fixed now. Sigh.

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