Explicit package name and masking earlier declarations in the same statement

I tried to write a perl version of the following algorithm

Here is the code that I have:

    #!/usr/bin/perl
    use waings;
    use strict;
    use diagnostics;  

    my $s1 = 'GATTACCA'; 
    my $s2 = 'AGTGGGCGGGGAGAGAGAGAGAGG'; 

    my $dist = levdist($s1, $s2); 

    sub levdist 
    { 
        my ( $seq1, $seq2 ) = (@_)[0,1]; 

        my $l1 = length($s1); 
        my $l2 = length($s2); 
        my @s1 = split '', $seq1; 
        my @s2 = split '', $seq2; 

        for (my $i = 0; $i <= $l1; $i++) { 
            my $distances->[$i]->[0] = $i; 
        } 
        for (my $j = 0; $j <= $l2; $j++) { 
            my $distances->[0]->[$j] = $j;
        }
        for (my $i = 1; $i <= $l1; $i++) {
            for (my $j = 1; $j <= $l2; $j++) {
                if ( $s1[$i-1] eq $s2[$j-1] ) {
                    my $cost = 0;
                } else {
                    my $cost = 1;
                }
                my $distances->[$i]->[$j] = minimum($distances->[$i-1]->[$j-1] + my $cost,
                                          $distances->[$i]->[$j-1]+1,
                                          $distances->[$i-1]->[$j]+ 1 )
            }
        }
        my $min_distance = my $distances->[$l1]->[$l2];
        for (my $i = 0; $i <= $l1; $i++) { my $min_distance = minimum($min_distance, my $distances->[$i]->[$l2]);
        }
        for (my $j = 0; $j <= $l2; $j++ ) {
            my $min_distance = minimum($min_distance, my $distances->[$l1]->[$j]);
        }
        retu $min_distance;
    }

    sub minimum
    {
        my $min = shift @_;
        foreach ( @_ ) {
            if ( $_ < $min ) {
                $min = $_;
            }
        }
        retu $min;
    }

This throws the following error:

    Global symbol "$distances" requires explicit package name at ./levenshtein.pl line 33.
    Global symbol "$distances" requires explicit package name at ./levenshtein.pl line 34.
    Global symbol "$distances" requires explicit package name at ./levenshtein.pl line 35. 

When I alter the code to look like:

    my $distances->[$i]->[$j] = minimum(my $distances->[$i-1]->[$j-1] + my $cost,
                                          my $distances->[$i]->[$j-1]+1,
                                          my $distances->[$i-1]->[$j]+ 1 

I get the following set of errors:

    "my" variable $distances masks earlier declaration in same statement at
     ./levenshtein.pl line 33 (#1)
     (W misc) A "my", "our" or "state" variable has been redeclared in the
     current scope or statement, effectively eliminating all access to the
     previous instance.  This is almost always a typographical error.  Note
     that the earlier variable will still exist until the end of the scope
     or until all closure references to it are destroyed.

     "my" variable $distances masks earlier declaration in same statement at
./levenshtein.pl line 34 (#1)
     "my" variable $distances masks earlier declaration in same statement at
./levenshtein.pl line 35 (#1)

I feel like I am in a catch-22. I get an error if I declare the variable or not. Any insights would be appreciated. Thanks,