However, using {m,n} only allows me to match a maximum of 9 times

Oh really? What version of Perl are you using?

% perl -le 'print shift()=~/^ab{20,30}$/ ? "yay" : "nay"' abb
nay
% perl -le 'print shift()=~/^ab{20,30}$/ ? "yay" : "nay"' abbbbbbbbbbb
+bbbbbbbbb
yay
% perl -le 'print shift()=~/^ab{20,30}$/ ? "yay" : "nay"' abbbbbbbbbbb
+bbbbbbbbbbbbbbbbbbbbbb
nay
[download]

Works for me...