I was looking at the Time::localtime module and noticed that it overloaded perl's built-in, localtime(). I was wondering how it it worked.

Looking to the internals, it seemed to me that it just exported (via Exporter) it's localtime() function. Nothing special. When I tried that, however, it didn't work.

Try as I might, I could not get my module to overload the built-in in the use'ing program. I thought I understood exporting fairly well. I even tried exporting by hand (via typeglob assignment, see The Second Try below) to no avail. (I know I'm doing this correctly because it works for variables and non-built-in functions.)

As far as I can tell, Time::localtime is not doing anything special besides exporting the function. There must be something I'm missing!

I've included a simple test program and two modules (the Exporter version and the typeglob version) below, as well as the output I get from the program and what the output should be.

Can anyone please help me to understand what's going on here and what I'm doing wrong?
Thanks!

#!/usr/bin/perl -w

use strict;

use lib '.';
use MyTest;

my $x = "blah blah blah\n";
chomp($x);
print "^$x\$\n";
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package MyTest;
use strict;

BEGIN {
    use Exporter ();
    use vars qw(@ISA @EXPORT);
    @ISA = qw(Exporter);
    @EXPORT = qw(chomp);
}

sub chomp(@) {
    my $str = shift;
    CORE::chomp($str);
    return $str . "_this is a test";
}

1;
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package MyTest;
use strict;

sub import {
    *main::chomp = \&MyTest::chomp;  # Doesn't work
#    *::chomp     = \&MyTest::chomp;  # Doesn't work either
#    *CORE::chomp = \&MyTest::chomp;  # Nope
#    *main::chomp = \*MyTest::chomp;  # Sorry, no go
#    *::chomp     = \*MyTest::chomp;  # I wish
#    *CORE::chomp = \*MyTest::chomp;  # Please, give it up
}

sub chomp($) {
    my $str = shift;
    CORE::chomp($str);
    return $str . "_this is a test";
}

1;
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