this should do what you want. also, it will work if a zero value is found in the data, which fails with your current test. i've included some test data and examples.

#!/usr/bin/perl
use strict;
use warnings;
$|++;


sub to_zero_or_below 
{
    ## must have a two element list to process
    return unless 2 <= @_;
    for my $index ( 1..$#_ )
    {
        ## skip unless i've decended to zero or below
        next unless $_[$index - 1] > 0 and $_[$index] <= 0;
        ## return the remainder of the list
        return @_[$index..$#_];
    }
}

my @data= ( -3, -1, 1, 3, 2, 1, 0, -1, -2 );

## zero present
print $_, $/ 
    for to_zero_or_below( @data );

print "~~~\n";

## no zero
print $_, $/
    for to_zero_or_below( reverse @data );
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