use strict;
use warnings;

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

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

my $replacement_func = sub { "<test>" . $1 . "<\/test>"; };
# OR my $replacement_func = sub { "<test>$1<\/test>"; };
my $second_test = replace_with_dynamic($test_data, $pattern, $replacement_func);

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

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

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

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

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