thanks but even if the code below runs well with all your improvements, as soon as i add a simply print "\@arr [@arr]\n"; at the end, the program hangs, eating a lot of memory. I dont understand why.

use strict;
use warnings;

sub trigger{print "Triggered: ",map {defined $_ ? " $_" : 'UNDEF'}@_,"
+\n"}

{
 package Arraytrigger;
 use Tie::Array;
 use vars qw(@ISA);
 @ISA = ('Tie::StdArray');

 for (qw(STORE CLEAR PUSH POP SHIFT UNSHIFT)) {
        my $s = "SUPER::$_";
        no strict 'refs';
        *$_ = sub { &main::trigger; shift()->$s(\@_) };
    }
}

#package main..

tie my @arr, 'Arraytrigger';

print "\tSetting list:\n" and @arr = qw(a b c d e);
#print "\tSetting one:\n"  and $arr[0]=0;
#print "\tpushing:\n"      and push @arr,'f';
#print "\tpopping:\n"      and pop @arr;
#print "\tshifting:\n"     and shift @arr;
#print "\tunshifting:\n"   and unshift @arr, 'zero';
#print "\tclearing with undef \@arr:\n"     and   undef @arr;
#print "\tSetting list:\n" and @arr = qw(a);
#print "\tSetting list:\n" and @arr = qw(a);
#print "\tclearing with \@arr=():\n"     and   @arr=();
#my $ref = \$arr[0];
#print "\tsetting by reference:\n"     and   $$ref=11;
#print "\tclearing:\n"     and   @arr=();#undef @arr and @arr=undef se
+em no good..e


# print "\@arr [@arr]\n";
#use Data::Dump;print dd(@arr);
[download]

thanks
L*