In the interests of completeness, here's an ST implementation (update: with alphabetic case folding)

my @g = qw(St1 St10 St2 St12 St6 St8 ab3 ab0 st5);

my @b =
  map { $_->[2] }
  sort{ lc $a->[0] cmp lc $b->[0] || $a->[1] <=> $b->[1] }
  map { [/(\D*)(\d*)/, $_] } @g;

foreach my $x (@b){
    print "$x\n";
}
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See Schwartzian Transform and Advanced Sorting - GRT - Guttman Rosler Transform for more info