This answer is explicitly for the question tag and not for the specific environment which the user has posted the question for python 2.5 or python 2.6:
How can I specify the version of Python that Perl's Inline::Python module is using?
=> when your OS has both python 3.x and python 2.x it picks up the python that is shown when you type python in your terminal/command line.
So when you have to choose between 3.x and 2.x Makefile.PL will not ask you the question instead it'll pick the one with python (usually python2.x with ubuntu where python will give us python2.x)
Solution: in Makefile.PL change $p value to "/python3" as shown below and it'll choose the right python version.
Note: to make this changes you need to install perl packages by this method click here
#============================================================================
# What python are we going to try?
#============================================================================
my @pythons;
my $sep = $^O eq 'MSWin32' ? ";" : ":";
for $p (split /$sep/, $ENV{PATH}) {
$p =~ s/^~/$ENV{HOME}/;
$p .= "/python3";
push @pythons, { path => $p } if -f $p && -x $p;
}