You should only have to read each file once. From the way your describe your algorithm, you want to find things in one file but are not in another. The basic idea is this: 
my %seen;
open(B, "brd_sym_pn.txt") or die "...";
while (<B>) {
  my ($RefDes, $Pnumm, $Pkg_Type) = ...parse these from the line...
  $seen{$RefDes, $Pnumm, $Pkg_Type} = 1;
}
close(B);

open(S, "sym_text_latest.txt") or die "...";
while (<S>) {
  my ($RefDes, $Pnumm, $Pkg_Type) = ...parse these from the line...
  $seen{$Refdes, $Pnumm, $Pkg_Type} += 2;
}
close(S);

while (my ($key, $val) = each %seen) {
  if ($val == 1) {
    # $key is in first file but not second
  } elsif ($val == 2) {
    # $key is in second file but not first
  } else {
    # key is in both files
  }
}

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For info on how to interpret $key, have a look at the documentation for the $; variable in perldoc perlvar. For special cases you can optimize this code.

In reply to Re: compare data between two files using Perl by pc88mxer
in thread compare data between two files using Perl by steveb94553

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