G'day IruP,

Welcome to the Monastery.

The following achieves what you ask; however, you've not been clear on what exact formats the keys, and values for the arrayrefs, take. So, the following code shows the basic technique; but, when you have a better specification, the specific elements of the code may well need to be changed.

#!/usr/bin/env perl

use strict;
use warnings;

use Data::Dump;

my @array = ('a', 1, 2, 3, 4, 'b', 6, 7, 8);

my %hash;

my $key;

for my $element (@array) {
    if ($element =~ /^\D$/) {
        $key = $element;
    }
    else {
        push @{$hash{$key}}, $element;
    }
}

dd \%hash;
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Output:

{ a => [1 .. 4], b => [6, 7, 8] }
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See Data::Dump if you're unfamiliar with that module; the builtin Data::Dumper module has similar functionality.