[027#2]

1 files changed, 45 insertions, 0 deletions

diff --git a/027/ch2.pl b/027/ch2.pl
new file mode 100755
index 0000000..25bd645
--- /dev/null
+++ b/027/ch2.pl
@@ -0,0 +1,45 @@
+#!/usr/bin/env perl
+#
+# Write a script that allows you to capture/display historical data. It could be
+# an object or a scalar. For example
+#
+#   my $x = 10; $x = 20; $x -= 5;
+#
+# After the above operations, it should list $x historical value in order.
+################################################################################
+
+use strict;
+use warnings;
+
+{
+    package Hist;
+
+    require Tie::Scalar;
+    our @ISA = qw<Tie::Scalar>;
+
+    sub TIESCALAR {
+        return bless \my @histogram, shift;
+    }
+    sub FETCH {
+        my @self = @{shift()};
+        printf STDERR "History of values: %s\n", join(", ", @self);
+        return @self[@self-1]
+    }
+    sub STORE {
+        my $self = shift;
+        my $value = shift;
+        push @$self, $value;
+    }
+}
+
+tie my $x, 'Hist';
+
+$x = 10;
+$x = 20;
+$x = -5;
+
+my $y = $x;
+print "y=$y\n";
+
+$x = 200;
+print "x=$x\n";