Null character appearing when I print a file - perl

Question

I have a code where I read a file and remove a block of line if a certain keyword matches. If I see the key word THERMST, I delete the line before and all lines until I reach a & :
QNODE "CExtHrn - Heater_Bidon" 1.0 T884 TOTAL
THERMST "CExtHrn" 0 2.500000E+01 3.000000E+01 883 ID 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 "Heater_Bidon"
NAME2 Heater_ CExtHrn - Heater_Bidon
NAME Heater_ 40097 40170 1
TABTYPE 884 TABLE OPERATION
TABDATA 884 885 INTERP
TABDATA 884 883 THERMST
TABTYPE 885 QNODE TIME
TABDATA 885 2.000000E+01 0.000000E+00
$
However, for an obscure reason, when I print to a new file, it gives several null characters on a certain line. The weird thing is that this line is not related with the line I just changed. If I don't modify the file, by commenting the following lines, I don't get any null characters.
# We delete the last 2 line and skip the rest of the qnode/thermst definition
splice #INPF1_OUT, -2;
# Skipping the lines until next comment line.
$ii++ until substr($INPF1_IN[$ii], 0, 1) eq '$';
$ii = $ii - 1;
Any idea what this could be? The null characters are causing problems for what I do with the file.
Here is what the line should be :
NAME winte_T 101269 101270 1
here is what it prints in the new file :
NAME winte_T ULNULNULNULNULNULNULNULNULNULNULNULNULNULNULNULNULNULNULNULNULNULNULNULNULNULNULNULNULNULNULNULNULNULNULNULNULNULNULNULNULNULNUL 101269 101270 1
You can see that the line that cause the error is not related to the one that should be modified
Thank you, the code is below
#!/bin/perl
use strict;
use Text::ParseWords;
open (INPF1_in, '<', $INPF1)
or die "Not able to open : $INPF1";
my #INPF1_IN = <INPF1_in>;
close INPF1_in;
my #INPF1_OUT; # Output INPF1
my $cardno = 1;
my $ii = 0;
until ($ii > $#INPF1_IN) {
my $INPF_line = $INPF1_IN[$ii];
push(#INPF1_OUT, $INPF_line); # Adding line
chomp($INPF_line);
if ($INPF_line eq "-1") {
$cardno++;
}
if ($cardno == 9) {
my #line = parse_line(" ", 0, $INPF_line); # parsing the line elements
if ($line[0] eq "THERMST") { # If Thermostat
# We delete the last 2 line and skip the rest of the qnode/thermst definition
splice #INPF1_OUT, -2;
$ii++ until substr($INPF1_IN[$ii], 0, 1) eq '$';
$ii = $ii-1; # Skipping the lines until next comment line.
}
}
$ii++;
}
open (INPF1_out, '>', $INPF1);
print INPF1_out $_ foreach #INPF1_OUT;
close INPF1_out;

Answer 1

I may be misreading your code, but it look like you're trying to do something very simple in perl, a very hard way.
If I'm reading it right, what you're trying to do is take an input record format, and conditionally print certain lines. Perl has a very good tool for this, called the 'range operator'.
I think you will be able to accomplish what you want with something considerably simpler.
#!/bin/perl
use strict;
use warnings;
while ( <DATA> ) {
print unless ( m/^THERMST/ ... m/^\$$/ );
}
__DATA__
QNODE "CExtHrn - Heater_Bidon" 1.0 T884 TOTAL
THERMST "CExtHrn" 0 2.500000E+01 3.000000E+01 883 ID 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 0.000000E+00 "Heater_Bidon"
NAME2 Heater_ CExtHrn - Heater_Bidon
NAME Heater_ 40097 40170 1
TABTYPE 884 TABLE OPERATION
TABDATA 884 885 INTERP
TABDATA 884 883 THERMST
TABTYPE 885 QNODE TIME
TABDATA 885 2.000000E+01 0.000000E+00
$
This is an example, based on the data you've given so far - if you can give a bit more to show exactly what you're trying to accomplish, I would be pretty sure you can extract the information you need without having to do iterating through elements in an array of words. Perl can do better than that.
(I am guessing a bit, as it's completely unclear where you're getting $cardno from. However this should be quite easy to modify to suit your needs)