I see hdb has shown the syntax you requested. Be aware that splice can be slow and there are often better alternatives. For instance, if you had intended to use splice to remove lowercase characters, you could have rewritten that entire block of code above as:

for (@MainArray) {
    @$_ = grep { ! /[a-z]/ } @$_;
}
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Here's my test:

#!/usr/bin/env perl

use strict;
use warnings;

use Data::Dumper;

my @MainArray;

# Original array populating code
while (<DATA>) {
    chomp;
    push @MainArray, [ split // ];
}

# New alternative to 'splice' code
for (@MainArray) {
    @$_ = grep { ! /[a-z]/ } @$_;
}

print Dumper \@MainArray;

__DATA__
Hello
my
name
is
Jack
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Output:

$ pm_file_chars_to_AoA_2.pl
$VAR1 = [
          [
            'H'
          ],
          [],
          [],
          [],
          [
            'J'
          ]
        ];
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Ohke, so I now have this

open (A1, "<An1.txt") or die "can't open";
open (A2, "<An2.txt") or die "can't open";

my @array1;
my @array2;

while (<A1>)
{
    my $in = $_;
    chomp $in;
    push (@array1, [split(//, $in)]);
}

while (<A2>)
{
    my $in = $_;
    chomp $in;
    push (@array2, [split(//, $in)]);
}

my $length = $#array1;
my $total = 0;
for (my $x = 0; $x <= $length; $x++)                                  
+    
{
    my $smallLength = scalar(@{$array1[$x]});
    for(my $q = 0; $q <= $smallLength; $q++)
    {   
        if($array1[$x][$q] =~ /^(\+|\_)$/ && $array2[$x][$q] =~ /^[A-Z
+a-z]$/)                    
        {
            splice(@{$array2[$x]}, $q, 0, ''); 
        }
        
        if($array2[$x][$q] =~ /^(\+|\_)$/ && $array1[$x][$q] =~ /^[A-Z
+a-z]$/)                    
        {                                                             
+        
            splice(@{$array1[$x]}, $q, 0, ''); 
        }
        $total++;
    }
}
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I am trying to compare and calculate the diffence between to text files. Calculations come later in my code but that is not important. I get error message 'Use of uninitialized value in pattern match (m//)' for the 2 IF statements. Any idea why?

Firstly, this is veering completely off-topic. Further, the default depth for viewing threads is Re^3 so most won't even view this new question. Start a new thread when you have a new question - you can always add a link to a previous thread if it has supporting information.

You have an off-by-one error. An array of 10 elements has indices in the range 0 to 9. In the outer loop, you're checking the correct range with 0 to $#array1; in the inner loop you're checking past the end of the array: 0 to scalar(@{$array1[$x]}).

-- Ken

splice( @{ $MainArray[$x] }, $q, 1 );
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