use strict;
use warnings;
#this scripts we define the first variable: SCALAR, $
#the use strict and use warnings are methods that provide strict definition of variables and give warnings when some errors happen. 


my $id1="whatever_id1";
# "my" define a variable in our script. the content of scalar is defined by the double quotation  
my $seq1="ATAATROFHJKDGHJFKFGDHJK";
my $id2=$id1; 
my $seq2="ATAATROFHJKDGHJFKFGDHJKPLUS"; 





print $id1 eq $id2, "\n";
# "eq" is test for whether scalar is identical. similarly you test whether not equal (ne), less or equal than (le, <=), less than (lt, <), greater than (gt, >) and greater or equal than (ge, >=)
print $seq1 eq $seq2, "\n"; 
print length($seq1) le length($seq2), "\n";
#length test the length of scalar. 
print length($seq1) lt length($seq2), "\n";
print $id1, "\n";
print $seq1, "\n";
my $new_seq=$id1." ".$seq1; 
#"." connects scalars;
print $new_seq, "\n";
print length($new_seq),"\n";
print substr($new_seq, 4,18), "\n";
#substr gives a partial string which starts from one position that extends to the defined end.