perl: refer to groups in foreach loop - regex

Question

Can I refer to groups in a foreach loop? my code below works:
#SEP_line=grep(/,\s(SEP[A-F0-9]*),\s(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}),\s(\+\d+),\s.*,\s(\w+)\n$/, #lines);
foreach (#SEP_line)
{
/,\s(SEP[A-F0-9]*),\s(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}),\s(\+\d+),\s.*,\s(\w+)\n$/;
print $1.",".$2.",".$3.",".$4."\n";
}
Since I already specified the match regex in #SEP_line definition, I'd do something like this:
#SEP_line=grep(/,\s(SEP[A-F0-9]*),\s(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}),\s(\+\d+),\s.*,\s(\w+)\n$/, #lines);
foreach (#SEP_line)
{
print #SEP_line[$1].",".#SEP_line[$2].",".#SEP_line[$3]."\n";
}
This doesnt work. Thanks in advance

Answer 1

Why loop twice (grep, foreach)? You can do it all in one loop:
foreach my $line (#lines)
{
if ($line =~ /,\s(SEP[A-F0-9]*),\s(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}),\s(\+\d+),\s.*,\s(\w+)\n$/)
{
print "$1,$2,$3,$4\n";
}
}

Answer 2

Don't hand-parse and hand-generate CSV! It's simpler and cleaner to use a CSV parser.
use Text::CSV_XS qw( );
my $fh_in = ...;
my $fh_out = \*STDOUT;
my $csv_in = Text::CSV_XS->new({ binary => 1, auto_diag => 2, sep => ', ' });
my $csv_out = Text::CSV_XS->new({ binary => 1, auto_diag => 2 });
while ( my $row = $csv_in->getline($fh_in) ) {
$csv_out->say($fh_out, [ #$row[-4,-3,-2,-1] ]
if $row->[-4] =~ /^SEP[A-F0-9]*\z/
&& $row->[-3] =~ /^\d{1,3}(?:\.\d{1,3}){3}\z/
&& $row->[-2] =~ /^\+\d+\z/
&& $row->[-1] =~ /^\w+\z/;
}