An alternative is to use 'named parameters' instead. This is just a hack where we collect a hash from the parameter line (%args) and merge it into the defaults (%def below):

use warnings;
use strict;

test1(arg1=>'A1',arg3=>'A3',arg4=>'A4');
test1(arg1=>'B1',arg2=>'',arg3=>'B3',arg4=>'B4');

sub test1
{
    my %def = (arg1 => 'A1', arg2 => 'A2',
               arg3 => 'A3', arg4 => 'A4');
               
    my %args = (%def, @_);
    
    (keys %def != keys %args) and die "Invalid argument";
    
    local $, = ' ';
    print %args,"\n";
}
[download]

The output is:

arg2 A2 arg1 A1 arg4 A4 arg3 A3
arg2  arg1 B1 arg4 B4 arg3 B3
[download]

Passed argameters can be obtained from the hash using the parameter name as the key, for example $args{arg1}

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