TITS (Try It To See):

use strict;
use warnings;

for my $vmstr ("0", "01", "00", "000", "1", "10") {
    my ($digits) = "-$vmstr" =~ /-(\d+)$/;

    print "'$vmstr': \$digits '$digits'\n";
}
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Prints:

'0': $digits '0'
'01': $digits '01'
'00': $digits '00'
'000': $digits '000'
'1': $digits '1'
'10': $digits '10'
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which is not what I understood you to want. Try adjusting the match to /-0*(\d+)$/.