package CloseOver;

use strict;
use warnings;

my $FIXED_STRING = 'fixed_string';  # could be a constant
my %persistent = (42 => { $FIXED_STRING => 123 });

sub something {

    my ($x,
        ) = @_;

    $persistent{$x}{$FIXED_STRING} = rand;

    }

END {
    for my $k (keys %persistent) {
        print "$k: $persistent{$k}{$FIXED_STRING}\n";
        }
    }

1;