use strict;
my $str = 'LOG:69369,1,30,40,80,06,1
LOG:69369,1,30,40,C0,06,1
POS:69453,69576034,-19244227,1,0
LOG:69405,2,30,40,00,06,2
POS:69333,69576024,-19244235,1,0
LOG:69405,2,30,40,C0,06,2 ';
my $regex = qr/^(?:LOG:)(?:[^,]*,){4}(?!00?)([^,]*).*$/mp;
my $subst = '';
my $result = $str =~ s/$regex/$subst/rg;
print "The result of the substitution is' $result\n";
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Perl, please visit: http://perldoc.perl.org/perlre.html