Perl example code

Excercise 12

#!/usr/bin/perl
use strict;
use warnings;

#TASK: Write a program that has one function.
#Use a variable named “$some_variable” in this
#function and in the main body of the program.

#Prove that you can alter the value of 
#$some_variable in the function without
#changing the value of $some_variable in the 
#the main body of the program

#declare variables used in the main routine 
my $some_variable;
my $some_variable_changed_by_subroutine;

#main routine
$some_variable = 10;

print "i am in the main routine and some_variable is: $some_variable\n";
$some_variable_changed_by_subroutine = subroutine($some_variable);
print "i am in the main routine some_variable is now: $some_variable\n";
print "i am in the main routine some_variable_changed_by_subroutine is: $some_variable_changed_by_subroutine\n";



#a subroutine that uses a variable with the same name as a variable in the main routine
sub subroutine{
    my $some_variable;
	
	$some_variable = $_[0];
	
	print "i am in the subroutine and some_variable is: $some_variable\n";
	
	++$some_variable;
	
	print "i am in the subroutine and some_variable is now: $some_variable\n";
	
	return $some_variable
}

Excercise 13

#!/usr/bin/perl
use strict;
use warnings;

#TASK: Read lines from input file – 
#print lines that match a regular expression

#open input and output files
open(IN,"excercise13input.txt");
open(OUT,">excercise13output.txt");

#read the input file line-by-line
#for each line ask if it matches the regex
#print it in the output file
while(<IN>){
	chomp;
	if ($_ =~ /^ATG?C*[ATCG]+?A{3,10}$/) {
		print OUT "$_\n";
		print "$_\n";
	}
}

#close input and output files
close(IN);
close(OUT);
exit();

excercise13input.txt

#this is the regex that we are looking for in the lines below
#/^ATG?C*[ATCG]+?A{3,10}$/



ATGCCCAA
ATGCCCAAAA
ATGCCCAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
DDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD