There is a module that provides this facility:

use Sub::Override;
use strict;
use warnings;

$, = ' ';
$\ = "\n";

sub a{ 'a' }
sub b{ 'b' }
sub c{ 'c' }

sub d{ ( a, b, c ) };

print d();
{
    my $override = Sub::Override->new;
    $override->replace(a => sub { "changed" })
             ->replace(b => sub { "changed" })
             ->replace(c => sub { "changed" });
    print d();
}
print d();
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output:

a b c
changed changed changed
a b c

Tool completed successfully
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