use strict;
my $str = 'May 23 16:57:33 nostalgia-for-infinity sshd[8541]: Failed password for invalid user root from 8.8.8.8 port 123 ssh2 from 127.0.0.1 port 50594 ssh2';
my $regex = qr/^(\S+|\S+\s+\d+\s+\S+) (\S+ )?sshd\[\d+\]: Failed password for (invalid user |illegal user )?(\S*) from (\S+)( port \S+ \S+\s*)?/p;
if ( $str =~ /$regex/ ) {
print "Whole match is ${^MATCH} and its start/end positions can be obtained via \$-[0] and \$+[0]\n";
# print "Capture Group 1 is $1 and its start/end positions can be obtained via \$-[1] and \$+[1]\n";
# print "Capture Group 2 is $2 ... and so on\n";
}
# ${^POSTMATCH} and ${^PREMATCH} are also available with the use of '/p'
# Named capture groups can be called via $+{name}
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