It is important to show us the "crap" because that shows that you have at least made an effort. It is also important to show some of the data because a description may not be very clear. As you will have noticed from the earlier replies to your original message, we are inclined to grab an idea and run with it - even if it is hopelessly wrong.

After all that lecturing, here is a solution for you (I suggest you examine this carefully, then reply explaining how you think it works):

use warnings;
use strict;


while (<DATA>)
  {
  my $match = /(NP\s+)(U\s+)(Pu\s*)/i;
  last if ! ($_ = <DATA>);
  next if ! $match;
  
  chomp;
  my $NP = substr $_, $-[1], $+[1] - $-[1] + 1;
  my $N  = substr $_, $-[2], $+[2] - $-[2] + 1;
  (my $Pu = substr $_, $-[3]) =~ s/(\s)//g;;
  $NP =~ s/(\s)//g;
  $N =~ s/(\s)//g;
  
  print "NP $NP, N $N, Pu $Pu\n";
  }

__DATA__
000    NP          U          Pu
001    1.270000    000001     3.141000
002    Lev         N          Pu
003    0.13        000001     3.277118
004    NP          U          Pu
005    1.000220    000002     3.098761
006    Yac         S          Yb
007    10.33000    000001     90000000
[download]

Note that the sample data is given as part of the script so tht other monks can simply download the entire thing and run it to see that it works. The sample given prints:

NP 1.2700000, N 0000013, Pu 3.141000
NP 1.0002200, N 0000023, Pu 3.098761
[download]

A quick couple things. The first reason I didn't post code, or output, is because I couldn't figure out how to use the tags for presenting it and I felt like an idiot. Like I said I'm new, so thanks for bearing with me. In any event, here is what I had done:

#!/usr/local/bin/perl -w
print "Enter an output file to analyze: ";
    
chomp ($phoenix_out= <STDIN>);
open (OUTPUT_FILE, "$phoenix_out") or die "can't open $phoenix_out: $!
+";

while (<OUTPUT_FILE>) {
      chomp;
    if (/0 EID:      93237      /){
        print "$.\n";
        next;
        print "anything?\n";
        ($a, $b, $c, $d, $e, $f, $g, $h, $i, $j, $k, $l) = split;
        $ND243 = $i;
        print "The amount of Am243 is $ND243\n";
    } #else { print "$. Problem!" };
}
[download]

What I couldn't figure out was how to get it to go to the line after the data that I found. (I realized the line above the data was a unique line and that I could search for it directly). An example of the output is as follows:

0 EID:      93237      93238      93239      94240     
  ND : 1.8833E-06 3.1143E-09 9.6338E-07 1.9309E-05 
  WT%: 8.2146E-03 1.3642E-05 4.2377E-03 8.5291E-02
[download]

The data extends longer across the page, but in the interest of width I didn't include all of it, it's just the same pattern repeated. Lastly, my attempt to understand your file:

match according to NP, then white space, then U, then white space, then Pu ending ... case insensitive. Last if there is no more data? Also, next loop if there is a match? Is this what moves you to the next line down? Break up the current data into substrings, I can figure out what the nomenclature means although I don't know it offhand, I have books I can read it from. Print off the results.

Again, thank you for the help, sorry for sucking at my posts early on, and any clarifications you would like to provide would be much appreciated.

#!C:/Perl/bin
use strict;            # no warnings because using uninit values below
use Data::Dumper::Simple;


use vars qw ( @nomatch $I1 $I2 $I3 $L1 $L2 @data $i $j );
while (<DATA>)
   {
      push @data,$_ ;
   }

{  
   while (@data) 
      {
      $L2 = pop @data;
      chomp $L2;
      #print "\$L2 is: $L2\n";
      $L1 = pop @data;
      chomp $L1;
      #print "\$L1 is: $L1\n";

      #find the data here

      if ( $L1 =~ /
            \d\d\d      # three digits
            \s+         # one or more whitespace
            NP          # exact string, NP
            \s+         # one or more whitespace
            U           # exact string, U
            \s+         # one or more whitespace
            Pu          # exact string, Pu
            /x          # end match, extended
         && $L2 =~ /
            (\d\d\d)    # three digits
            \s+         # one or more whitespace
            (\d\.\d{6}) # digit, period, six digits
            \s+         # one or more whitespace
            (\d{6})     # six digits
            \s+         # one or more whitespace
            (\d\.\d{6}) # digit, period, six digits
            /x )
        {
          my $n1 = $1; $I1 = $2; $I2=$3; $I3=$4;
          print "\n\tIn linepair ENDING with $n1, NP: $I1, U: $I2, Pu:
+ $I3\n";
        } 
        else
        {
          push @nomatch,"\n\tNo match on lines    $L1\n\t\t\t and $L2\
+n";
        }
      }
print "\n\n\t No Match pairs follow\n";
warn Dumper (@nomatch);
}
__DATA__
000    NP          U          Pu
001    1.270000    000001     3.141000
002    Lev         N          Pu
003    0.13        000001     3.277118
004    NP          U          Pu
005    1.000220    000002     3.098761
006    Yac         S          Yb
007    10.33000    000001     90000000
008    NP          U          Pu
009    2.130000    000140     5.797712
[download]