You could also use a hash slice to associate the two arrays:

my @users = qw( alice bob charlie );
my @ids   = qw( 123 456 789 );

my %id_of;
@id_of{@users} = @ids;  # hash slice


use Data::Dumper;
print Dumper(\%id_of);
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Output

$VAR1 = {
          'alice' => '123',
          'charlie' => '789',
          'bob' => '456'
        };
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