Thank you for your response. I have been trying both options. Using your advice my script now reads: 
#!/usr/bin/perl

use strict;
use warnings;
my ($record, $date, $outfile, $station, $sstation, $linecnt, $pcntg, @
+values);

print "Processing \"$ARGV[0]\"...\n";
$date = $ARGV[1];
%stations = map{ $_ => 1 } @ARGV[ 2 .. $#ARGV];
$outfile = $date.".txt";
$outfile =~ s/ /-/;

print "For Date: $date and Station: $station\n\n";
$linecnt = `wc -l < $ARGV[0]`;
open (INFILE, $ARGV[0]);
open (OUTFILE, ">>", $outfile);

while (<INFILE>) {
   $pcntg = int (($. / $linecnt ) * 100) ;
   print "$pcntg %\r";
   chomp();
   $record = $_;
   @values = split (',',$record);
   $sstation = $values[5];
   $sstation =~ s/ //g;
   if( $values[0] eq $date && exists $stations{ $sstation } ) {
      print OUTFILE $record."\n";
#      print "xx".$values[5]."xx\n";
      print "Record written to $outfile...\n";
      last;
   }
}

print "\nFinished\n";
close (INFILE);
close (OUTFILE);

[download]
It has worked just yet and I get the following errors: 
[s1269452@burn MIDAS_DATA]$ perl bulk_reorder_2105.txt midas_wxhrly_19
+9901-199912.txt "1999-12-15 11:00" 19260
Global symbol "%stations" requires explicit package name at bulk_reord
+er_2105.txt line 10.
Global symbol "$stations" requires explicit package name at bulk_reord
+er_2105.txt line 14.
Global symbol "%stations" requires explicit package name at bulk_reord
+er_2105.txt line 27.
Execution of bulk_reorder_2105.txt aborted due to compilation errors.

[download]
I have tried tweaking it a bit but I haven't really got anywhere.

In reply to Re^2: Bulk Reading and Writing of Large Text Files by Sterling_Malory
in thread Bulk Reading and Writing of Large Text Files by Sterling_Malory

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