Bioperl Training Exercise 3

1. Create an array (@ids) of sequence identifiers, e.g. your favorite genes. (You’re encouraged to use the qw() operator.)
2. Print out the first element.
3. Print out the last element.
4. Print the array within a double-quoted string and see how Perl handles that.
5. Print that array again but with a comma and space between the elements
6. Print the array again with each ID on a separate line (loop construct)
7. Print the array again with each ID and index in the array (other loop construct)
8. Print out an array slice of the 2nd to 4th items within a double-quoted string
9. APrint the last index of the array
10. Assign a value to element with index 42 of the array and print the last index of the array again.
11. Print the elements on separate line again. Strange things happened, no ?

Solution

#!/usr/bin/perl use strict;   # create array my @id = qw/id1 id2 id3 id4 id5 id6 id7/;   # print out first element print "First: $id[0]\n";   # print out last element print "Last: $id[-1]\n";   # print array print "Array: @id\n";   # print array with comma and space in between print "Array: ", join( ', ', @id), "\n";   # Print the array again with each ID on a separate line (loop construct) foreach my $id (@id) { print "$id\n"; }   # Print the array again with each ID and index in the array (other loop construct) # there are other possibilities as well for (my $i = 0; $i < @id; $i++) { print "Element $i: $id[$i]\n"; }   # Print out an array slice of the 2nd to 4th items within a double-quoted string print "Slice: @id[1..3]\n";   # print the last index of the array print "Last index of '\@id' is $#id\n"; # this means that an alternative way to print last element is: # print "Last: $id[$#id]\n";   # assign a value to element with index 42 of the array and print the last index of the array again. $id[42] = 'id43'; print "Last index of '\@id' is $#id\n";   # Print the elements on separate line again for (0..$#id) { print "Element $_: $id[$_]\n"; }