Building on AnomalousMonk's "Prior to Perl version 5.14" example we can come up with this SSCCE:

use strict;
use warnings;

use Test::More tests => 3;

my $data     = {x => "Maria's"};
my $old      = \%$data;
my @allparms = sort keys %$data;
my @oldparms = @allparms;
my @expected = ("Maria''s");

my @result = map { (my $f = $data->{$_} || '') =~ s/'/''/g; $f } @allp
+arms;

is_deeply \@result, \@expected, "apostrophe's are doubled";
is_deeply $data, $old, '$data is unchanged';
is_deeply \@allparms, \@oldparms, '@allparms is unchanged';
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You can then extend $data and @expected to provide a more comprehensive set of test data to prove that the algorithm matches your needs. All of this assumes (contrary to expectation) that choroba's guess that this is actually an XY Problem is incorrect.