Like this?

use warnings;
use strict;

use Data::Dumper;


my @a;
my @b;


@a = (1..100);
@b = (1..8);

print Dumper ( divarray(\@a, \@b) );

@a = (1..5);
@b = (1..8);

print Dumper ( divarray(\@a, \@b) );


sub divarray
{
    my @a = @{shift @_};
    my @b = @{shift @_};
    my @c;
    
    my $i = 0;
    my $b = int(@a/@b)+1;

    for ( @a )
    {
        push @c, [] 
            if $i == 0 or $i % $b == 0;
            
        push @{$c[-1]}, $_;

        $i++;
    }
    
    return \@c;
}
[download]

Thinking about it for a minute, this is an improved version of the function:

sub divarray
{
    my @a = @{shift @_};
    my @b = @{shift @_};
    my @c;
    
    my $b = int(@a/@b)+1;

    while ( @a )
    {
        push @c, [splice (@a, 0, $b)];
    }
    
    return \@c;
}
[download]