What came to my mind was to use Tie::File, which lets you "access the lines of a disk file via a Perl array" without reading the whole file into memory. The code below is incomplete and untested, but it shows the logic of how I would approach this using Tie::File.
use strict;
use warnings;
use feature 'say';
use Tie::File;
my $input_file = shift;
my $output_file1 = shift;
my $output_file2 = shift;
my @lines;
tie @lines, 'Tie::File', $input_file or die "Unable to open file '$inp
+ut_file': $!";
my $index = 0;
open(my $fh1,">",$output_file1) or die "Unable to open file '$output_f
+ile1': $!";
open(my $fh2,">",$output_file1) or die "Unable to open file '$output_f
+ile1': $!";
while ($index <= $#lines) {
next if (); #insert logic to determine which lines are ignored
my $current_line = $lines[$index];
my $fh;
if () { #insert logic to determine that current line goes to firs
+t file
$fh = $fh1;
}
else { #assumes if not skipped and not for first file, goes to 2n
+d file
$fh = $fh2;
}
say $fh $lines[$index];
#if needed, modify next if statement to determine if current line
+requires
#copying the next 4 input file lines
if ($lines[$index] =~ m/SDP_CMD_WRSIZEDFULL/i) {
say $fh $lines[$index + 1];
say $fh $lines[$index + 2];
say $fh $lines[$index + 3];
say $fh $lines[$index + 4];
$index += 5;
next;
}
$index++;
}
untie @lines;
close($fh1);
close($fh2);