I'm not sure just how big each rule file is, but reading in all of the file seems wasteful when you only want the first part. To carry on with Laurent R's example, you could extract the header part in the first loop and save it into an array for processing later: 

my @headers;
for my $rulefile (@rulefiles){
    open my $INFILE, "<", $rulefile or die "Can't open  $rulefile $!";
    my $header;
    while ( my $line = <$INFILE> ) {
        # see if this line contains opening bracket
        if ( $line =~ m/\(/ ) {
            my $pos = index( $line, '(' );
            last unless $pos > 0;
            $header .= substr( $line, 0, $pos );
            last;
        }
        else {
            $header .= $line;
        }
    }
    close $INFILE;
    push( @headers, $header ) if $header;
}

for my $header ( @headers ) {
    print "\nHeader:\n$header\n";
    
    # now process the header
}

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In reply to Re: Scanning multiple files from Snort rules one by one and extracting a particular part to another file - File Handling by tangent
in thread Scanning multiple files from Snort rules one by one and extracting a particular part to another file - File Handling by edison.pioneer

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