Actually, the problem is your syntax is bizarre :)

To get the highest index of an array from a reference to it the syntax should be $#{ $aref } not $#{ @$aref } which you have. The fact that your code works silently, is probably a bug:)

#! perl -slw
use strict;

sub get_size{
       my ($aref ) = @_;
       return $#{@$aref};
}

my @a = ( 1..10 );

print get_size( \@a );

__END__
P:\test>322384
9

P:\test>perl -d 322384.pl

Loading DB routines from perl5db.pl version 1.22
Editor support available.

Enter h or `h h' for help, or `perldoc perldebug' for more help.

main::(322384.pl:9):    my @a = ( 1..10 );
  DB<1> s
main::(322384.pl:11):   print get_size( \@a );
  DB<1> s
main::get_size(322384.pl:5):            my ($aref ) = @_;
  DB<1> s
main::get_size(322384.pl:6):            return $#{@$aref};
  DB<1> s
main::get_size(322384.pl:6):            return $#{@$aref};
  DB<1> s
Bizarre copy of ARRAY in leave at 322384.pl line 6.
        main::get_size('ARRAY(0x19ede94)') called at 322384.pl line 11
Debugged program terminated.  Use q to quit or R to restart,
  use O inhibit_exit to avoid stopping after program termination,
  h q, h R or h O to get additional info.
  DB<1> Config::DESTROY(c:/Perl/lib/Config.pm:1198):
1198:   sub DESTROY { }
  DB<1> q


#### change $#{@$aref} to $#{ $aref }


P:\test>322384
9

P:\test>perl -d 322384.pl

Loading DB routines from perl5db.pl version 1.22
Editor support available.

Enter h or `h h' for help, or `perldoc perldebug' for more help.

main::(322384.pl:9):    my @a = ( 1..10 );
  DB<1> s
main::(322384.pl:11):   print get_size( \@a );
  DB<1> s
main::get_size(322384.pl:5):            my ($aref ) = @_;
  DB<1> s
main::get_size(322384.pl:6):            return $#{$aref};
  DB<1> s
main::get_size(322384.pl:6):            return $#{$aref};
  DB<1> s
9
Debugged program terminated.  Use q to quit or R to restart,
  use O inhibit_exit to avoid stopping after program termination,
  h q, h R or h O to get additional info.
  DB<1> q
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