If you're dealing with csv, then I strongly recommend using Text::CSV_XS. Said this...

#!/usr/bin/perl

$infile = @ARGV[0];
$outfile = "OK.txt"; 
$outfile2 = "ERROR.txt";      
@Filter = ('01005;01000','01005;01001','01005;01002','01005;01003');
$zaehler = 0;
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Hmmm no strict, no warnings. Now, that is too bad...

open(INFILE, "< $infile")
or
die "\nDatei $infile konnte nicht geoeffnet werden\n";
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Better:

open my $in, '<', $infile or
  die "Error message including \$!: $!\n";
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and ditto as above wrt the other opens.

while (<INFILE>) { print OUTFILE if /@Filter[0]/; }
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Huh?!?