print "$info->{columns}[-1]\n";
[download]

prints:

userName
[download]

See also References quick reference

$VAR1 = {   #Variable is a hashRef
          'table' => [  #One key is "table", 
                        # which gives an arrayref.
                     [  #The first element in that array 
                        #is another arrayref
                       'CredSMB.168', #Element 0  
                              # AKA $VAR1->{table}[0][0];
                       '168',
                       '1',
                       'Customer.1',  #Element 3
                       '',
                       'BNS-NA-CA-SMB-SCGLOBAL',
                       '3',
                       'SCGLOBAL',
                       'ip360scglobal'
                     ]
                   ],
          'columns' => [ #Another key is "columns", 
                         #which gives an arrayref.
                       'REFERENCE', # array element [0]
                       'id',
                       'type',
                       'customer',
                       'notes',
                       'name',
                       'authAlgorithm',
                       'domain',
                       'userName'
                     ]
        };
[download]

You might want to consider a simpler rearrangement:
Have a hash where the keys are what is currently in 'columns' and the values are what is currently in 'table'.
$rowHash->{id} = 168; for example.
Depending on how you want to use them, you could make an array of such hashes, or a hash of those hashes (with the keys being some unique combination of data, such as the ID).

By having just a hash of hashes, you can manipulate the "table rows" much easier.

$rowHash = {id=>168, name=>'Jack'}; # create row
$tableHash->{$rowHash->{id}} = $rowHash; # add row to table
delete $tableHash->{$rowHash->{id}};  # delete row from table
$tableHash->{168}{name} = 'Jill'; #update single value
[download]

Thank you, actually i have no control over the data structure it's being returned from a call i simply need to get at what is there. re arrangement isn't an option. but thanks # AKA $VAR1->{table}[0][0]; is exactly what i needed. And to everyone else, thanks, i haven't been to this site in a number of years, but my memory was that the memebers were always extremely helpful and you still are!

#!/usr/bin/perl
use strict;
use warnings;

my $VAR1 = {
          'table' => [
                     [
                       'CredSMB.168',
                       '168',
                       '1',
                       'Customer.1',
                       '',
                       'BNS-NA-CA-SMB-SCGLOBAL',
                       '3',
                       'SCGLOBAL',
                       'ip360scglobal'
                     ]
                   ],
          'columns' => [
                       'REFERENCE',
                       'id',
                       'type',
                       'customer',
                       'notes',
                       'name',
                       'authAlgorithm',
                       'domain',
                       'userName'
                     ]
        };
foreach my $i (0 .. $#{$VAR1->{columns}}) {
    if ($VAR1->{columns}[$i] =~ /^userName$/) {
        print "$VAR1->{table}[0][$i]\n";
    }
}
[download]

See perlref, perlreftut, perllol and/or perldsc for some refreshers.

You mau find How can I visualize my complex data structure? useful.

@columns= @{$info->{columns}};
[download]