how to access a multidimensional array in Perl

So first we need to build a multidimensional array, the best way I know to do this in Perl is using references:

use strict;
use warnings;

open( my $fh, "<", "data" );
my @rows;
while ( my $line = <$fh> ) {
    chomp $line;
    my @row = split(':', $line) ;
    push( @rows, \@row );
};

The \ operator in \@row means that each element of the list @rows is actually a reference to another list @row. This allows for the sort of nested indexing which you seem to be seeking, like so:

`/bin/kish -x /home/whatever/testscript $rows[0]->[0] $rows[0]->[1] $rows[0]->[2]`

First we index into the list as usual (this is the "row" number). The arrow operator -> dereferences the reference to the list, then we index into that dereferenced list with the appropriate "column" number

while ($line=<FILEHANDLE>) {
    @letters=split(/\W+/,$line);
    system("/bin/kish -x /home/whatever/testscript $letters[0] $letters[1] $letters[2]");
}

You will need to open FILEHANDLE first. The while() loop (first) reads the file, one line at a time. The second takes the line, breaks it into chunks (non-alphanumeric characters [such as ":"] are used to define the breaks between the chunks). The system line runs the command itself. The last line "}" shows where the loop ends.