use Data::Trace;

my $data = {a => [0, {complex => 1}]};

sub BadCall{ $data->{a}[0] = 1 }

Trace($data);

BadCall();  # Shows stack trace of where data was changed.

use Data::Trace;
Trace();    # 1 level.
Trace(5);   # 5 levels.

Trace( \$scalar, @OPTIONS );
Trace( \@array , @OPTIONS );
Trace( \@hash , @OPTIONS );
Trace( $complex_data , @OPTIONS );

Trace( @OPTIONS );

-clone => 0,    # Disable auto tying after a Storable dclone.

-var => REF,    # Variable to watch.
REF             # Same as passing a reference.

-levels => NUM  # How many scope levels to show.
NUM             # Same as passing a decimal.

-raw => 1,      # Include Internal call like Moose,
                # and Class::MOP in a trace.
-NUM            # Same as passing negative number.

-message => STR # Message to use for a normal (non-
                # tie stack trace).
STR             # Same as passing anything else.

-methods => STR   # Monitors only specific methods.
-methods => [STR] #

Allows calling Trace like:
Trace() and Trace(-levels => 1) to
mean the same.

perldoc Data::Trace

The Artistic License 2.0 (GPL Compatible)