Binary search and selection sort in Perl

* Create 01_binary_search.pl

* Typo fixed in 01_binary_search.pl

* Create 01_selection_sort.pl

01_introduction_to_algorithms/perl5/01_binary_search.pl

@@ -0,0 +1,43 @@
+sub binary_search {
+
+    my ( $item, @list ) = @_;
+
+    # The borders inside where we are searching in:
+    my $low  = 0;
+    my $high = $#list;
+
+    # Do that until found or until just one element remains:
+    while ( $low <= $high ) {
+
+        # Detect the middle of the array:
+        my $mid = int( ( $low + $high ) / 2 );
+        my $guess = $list[$mid];
+
+        # We found it out:
+        if ( $guess == $item ) {
+            return $mid;
+        }
+
+        # The guess is too high, decrease it:
+        elsif ( $guess > $item ) {
+            $high = --$mid;
+        }
+
+        # The guess is too low, increase it:
+        else {
+            $low = ++$mid;
+        }
+    }
+
+    # Nothing at all found:
+    return 'None';
+
+}
+
+my @my_list = qw /1 3 5 7 9/;
+
+# Should display "1":
+print binary_search( 3, @my_list ), "\n";
+
+# Should display "None":
+print binary_search( -1, @my_list ), "\n";