You could use the \x to make your code more readable.

use strict;
my $x='Mr. Popcorn Dave';
print "Name valid\n" if m/^\s*         #ZERO OR MORE SPACES
                    (M(s|rs?|iss)\.?\s+)?  #POSS SALUTATION
                    [A-Z]+\.?\s+           #NAME AFTER SAL.
                    [A-Z]+                 #2nd NAME 
                    \s*([A-Z]+\s*)?$/ix;      #SUFFIX
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I have changed a couple of things,but I mainly I think it is clearer if you have \s* instead of (\s+)? and use the \x so that when you look back at this latter you have an idea of what each part of this regex does.