my system details
OS:Debian GNU/Linux 4.0
Kernel:2.6.18-4-686 GNU/Linux
Perl: 5.8.8 

##</code><code>##

$ locate Select.pm
/usr/lib/perl/5.8.8/IO/Select.pm
/usr/share/perl/5.8.8/Pod/Select.pm
/usr/share/perl5/Debconf/AutoSelect.pm
/usr/share/perl5/Debconf/Element/Dialog/Select.pm
/usr/share/perl5/Debconf/Element/Editor/Select.pm
/usr/share/perl5/Debconf/Element/Gnome/Select.pm
/usr/share/perl5/Debconf/Element/Kde/Select.pm
/usr/share/perl5/Debconf/Element/Noninteractive/Select.pm
/usr/share/perl5/Debconf/Element/Select.pm
/usr/share/perl5/Debconf/Element/Teletype/Select.pm
/usr/share/perl5/Debconf/Element/Web/Select.pm
/usr/share/perl5/HTML/Widget/Element/Select.pm

I will open the below module in vim editor


$vim /usr/lib/perl/5.8.8/IO/Select.pm

just search the pattern /b can_read
I have got this
sub can_read
{
 my $vec = shift;
 my $timeout = shift;
 my $r = $vec->[VEC_BITS];

 defined($r) && (select($r,undef,undef,$timeout) > 0)
    ? handles($vec, $r)
    : ();
}
after seeing this I will know what can_read can do.
I have done this for lot of perl modules and I have learnt some efficient techniques in this process, I am still learning, this is just my tips to you.