use strict;
my $str = 'Dr. RICHARD, MM
Dr. BOBBY Richard Klaus, MM
Richard, MM';
my $regex = qr/^(?:\s*(?:Dr[sa]?|Prof|M\.Ag|M[EM])\.?)+\s*|\s*,(?:\s*(?:Dr[sa]?|Prof|M\.Ag|M[EM])\.?)+$/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