Basic Perl Grammar
# : program statement to improve understanding of the program. It is ignored when you run the program
-w : It enables to print out error message when you make an error.
print : It prints out the following character string, number to your monitor
\n : new line character. It designates the end of a line of text and the start of a new line
Variable : The place to store data
1. $ : Scalar, to store specific number or character string
2. @ : Array, to store several values in sequence
3. % : Associative array, dataset without sequence
= : Assignment operator to give a value to the variable
To open a file using perl program
<STDIN> : The link between perl program and file. We can get the values from a file using this standard input device
Ex) $DNAfilename = <STDIN>;
chomp $DNAfilename; : To remove the last new line character when you input your filename
open(DNAFILE, $DNAfilename); : to open a file, we have to make a link between perl program and the file using open function
$DNASeq = <DNAFILE>; : to read the open file - we can only read one line using scalar variable
while : to read the whole lines in a file
Ex) while( $DNASeq = <DNAFILE> )
close DNAFILE; : to close the open file
exit; : Instruction for end of the program
* Another way to read whole lines in a file - use array variable (@)
Ex) @DNASeq = <DNAFILE>; : Array variable consists of n components.
First line will be stored in a first component and second line will be stored in a second component and so on.
use strict; : to check typing errors
use warnings; : to make easy debugging ( find and modify errors )
subroutine : to make a module and utilize it in main program (we can use it anytime)
basic structure of subroutine :
sub subroutine name {
execute statement
}
