I have no idea if thats how it should sort , but this is how you would cache your solution (also known as schwartzian transform) to save on redundant split and s// (save CPU by using more memory)

#!/usr/bin/perl --
use strict; use warnings;
use Data::Dumper;
my @unsorted = split /[\r\n]+/, <<'__THE_DATA__';
ID12-ABC-5.1
ID9-ABC-5.1
ID3-ABC-6.1
ABC-5.1
ID12-ABC-5.1.5
ID15-ABC-6.1
ABC-6.1
ID5-ABC-5.1
ID5-ABC-5.1.5
ABC-5.1.5
__THE_DATA__

print Dumper( \@unsorted );


my @sorted = sort { 
   @{[(split('-',$b))]}[0] =~ s/\d+// cmp @{[(split('-',$a))]}[0] =~ s
+/\d+// ||
   (split('-',$b))[-1] cmp (split('-',$a))[-1]
   } @unsorted;

print Dumper( \@sorted );

@sorted = map { $_->[0] } sort {
    $b->[1] cmp $a->[1]
    ||
    $b->[2] cmp $a->[2]
} map {
    my(@f) = split /-/, $_;
    [
        $_,
        scalar( $f[0] =~ s/\d+// ),
        $f[-1],
    ];
} @unsorted;

print Dumper( \@sorted );

__END__
$VAR1 = [
          'ID12-ABC-5.1',
          'ID9-ABC-5.1',
          'ID3-ABC-6.1',
          'ABC-5.1',
          'ID12-ABC-5.1.5',
          'ID15-ABC-6.1',
          'ABC-6.1',
          'ID5-ABC-5.1',
          'ID5-ABC-5.1.5',
          'ABC-5.1.5'
        ];
$VAR1 = [
          'ID3-ABC-6.1',
          'ID15-ABC-6.1',
          'ID12-ABC-5.1.5',
          'ID5-ABC-5.1.5',
          'ID12-ABC-5.1',
          'ID9-ABC-5.1',
          'ID5-ABC-5.1',
          'ABC-6.1',
          'ABC-5.1.5',
          'ABC-5.1'
        ];
$VAR1 = [
          'ID3-ABC-6.1',
          'ID15-ABC-6.1',
          'ID12-ABC-5.1.5',
          'ID5-ABC-5.1.5',
          'ID12-ABC-5.1',
          'ID9-ABC-5.1',
          'ID5-ABC-5.1',
          'ABC-6.1',
          'ABC-5.1.5',
          'ABC-5.1'
        ];
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