fauria:

Your regex, "/M.?c*/" will do fine at finding "Mac" or "Mc" and printing the REST of the name (rather than what the OP sought), and recall that c* matches ZERO OR MORE "c"s, meaning non-names, like Mccccc (ill-formatted roman numerals??) will match.

Also, as written, (without capturing parens) it prints:

Achallies
Achallies
Achounich
Achounich
Adam
Adam
Adie
Adie
Aindra

whereas (with slightly different use of quantifiers and a couple additional names as test cases), this appears to work as requested:

#!C:perl/bin

my @names = qw "M Mac McA Mcccccc MacAchallies McAchallies MacAchounic
+h McAchounich MacAdam McAdam MacAdie McAdie MacAindra";
 
for(@names){
   $_ =~ /(M.?c+.*)/ and print "$1\n";
}

=HEAD  output is:
Mac
McA
Mcccccc
MacAchallies
McAchallies
MacAchounich
McAchounich
MacAdam
McAdam
MacAdie
McAdie
MacAindra

=cut
[download]

Noted also, that using $' (and friends) incurs a lot of overhead.
And, just because they're not here, use strict; use warnings.