use strict;
use warnings;

my $test_data = 'This is some test data: $888...!';
my $pattern = qr{(\$?[0-9,]+)};

my $replacement = '<test>$1<\/test>';
my $first_test = apply_regex_e($test_data, $pattern, $replacement);

$replacement = 'q{<test>}.$1.q{<\/test>}';
my $second_test = apply_regex_ee($test_data, $pattern, $replacement);

print $first_test, "\n", $second_test;

sub apply_regex_e {
    my ($data, $pat, $rep) = @_;

    $data =~ s/$pat/$rep/e;
    return $data;
}

sub apply_regex_ee {
    my ($data, $pat, $rep) = @_;

    $data =~ s/$pat/$rep/ee;
    return $data;
}


##</code><code>##

This is some test data: <test>$1<\/test>...!
This is some test data: <test>$888<\/test>...!