Ah, ok, that was originally not clear from the question. You can use split to get the list from the string: 
#!/usr/bin/perl
use warnings;
use strict;

my %hash1 = (key1 => 'val1,val2',
             key2 => 'val3',
             );
my %hash2 = (val1 => 'val5,val6,val7',
             val2 => 'val8,val9',
             val3 => 'val3',
            );
my %result = map { $_ => join ',', map split(/,/, $hash2{$_}),
                                       split /,/, $hash1{$_}
                 } keys %hash1;

while (my ($k, $v) = each %result) {
    print "$k: $v\n";
}

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لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ

In reply to Re^5: how to use the values of the first hash to be the keys for the second hash by choroba
in thread how to use the values of the first hash to be the keys for the second hash by lrl1997

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