#/usr/bin/perl

use warnings;
use strict;

sub eval_string {
    my $string=shift;
    eval $string;
}

my $string1="
sub foo {
    print qq(first definition\n);
}

foo();
";
eval_string($string1);

my $string2="
sub foo {
    print qq(second definition\n);
}

foo();
";
eval_string($string2);

##</code><code>##

~>perl test.pl
first definition
Subroutine foo redefined at (eval 2) line 2.
second definition