I am trying to make a simple perl program that reads 20 characters upstream from the codon ATG in a given sequence. The following is what I have. I just dont know how to make the program read 20 characters upstream from the ATG codon.
print "\nThis program will read 20 characters upstream from the codon ATG in the given sequence.\n
Please, input your sequence: ";
my $sequence = <>;
chomp $sequence;
if ($sequence=~ m/ATG/g) {
print "The sequence is $sequence";
} else {
print "The given sequence doesn not contain ATG.\n"
}
exit;