How about

my $string = "PM123456789some more text";

my($chars, $nums, $rest) = $string =~ m{
  ^               # start of the string
  ( [a-z]{2} )    # capture 2 chars
  ( \d{9} )       # capture 9 digits
  ( .* )          # capture the rest
  \z              # end of the string
}ix;

print "chars: $chars", $/,
      "nums:  $nums",  $/,
      "rest:  $rest",  $/;

__output__

chars: PM
nums:  123456789
rest:  some more text
[download]

See man perlretut and man perlre for more info.
HTH

_________
broquaint