package Foo::Bar;

use Regexp::Assemble;

our $VERSION = '0.01';

sub new {
	my $class = shift;
	my $self = bless({@_}, $class);

	## precompile regexes
	$self->{regex} = Regexp::Assemble->new->add( 'some-stuff' )->re;

	return $self;
}

sub function {
	my $self;

...

	$var =~ $regex;
}


##</code><code>##

package Foo::Bar;

use Regexp::Assemble;

our $VERSION = '0.01';
our $regex = Regexp::Assemble->new->add( 'some-stuff' )->re;

sub function {
...
	$var =~ $regex;
}