Win8 Strawberry 5.8.9.5 (32)  Sat 10/01/2022 17:18:27
C:\@Work\Perl\monks
>perl

use strict;
use warnings;

use Data::Dump qw(dd);  # for debug

my $text = <<'TEXT';
Regular expressions have the undeserved reputation
of being abstract and difficult to understand.
TEXT
print "before ---$text--- \n";

my @regexlist = split /\n/, <<'REGEX';
a A
i I
e E
REGEX

my %replace = map split, @regexlist;
# dd \%replace;  # for debug

my ($rx_search) =
    map  qr{ $_ }xms,
    join ' | ',
    map  quotemeta,
    reverse sort
    keys %replace
    ;
# dd $rx_search;  # for debug

$text =~ s{ ($rx_search) }{$replace{$1}}xmsg;
print "after +++$text+++ \n";

^Z
before ---Regular expressions have the undeserved reputation
of being abstract and difficult to understand.
---
after +++REgulAr ExprEssIons hAvE thE undEsErvEd rEputAtIon
of bEIng AbstrAct And dIffIcult to undErstAnd.
+++