use strict;

my $seq1 = 'aabcdefg';
my $seq2 = 'aabcdefgabcde';

sub in_sequence
{
    my $str = shift;  # fetch the string value
    my $ok = 1;       # set private variable $ok = 1
    $str =~ m/(.)(.)(??{ $ok = 0 if $2 lt $1; 0 })/;
    return $ok;
}

print "Sequence is ", in_sequence($seq1)?"good":"bad", "\n";
print "Sequence is ", in_sequence($seq2)?"good":"bad", "\n";