Prototype mismatch: sub main::head ($) vs none

netscraps — Thu, 09 Jul 2009 18:12:45 +0000

Turns out that when you use the LWP::Simple & CGI modules together in a Perl script, each has a conflicting head() function that throws that error. Who knew? Everyone who didn’t take the time to read the CAVEAT note at the bottom of the LWP::Simple docs, apparently:

Note that if you are using both LWP::Simple and the very popular CGI.pm module, you may be importing a head function from each module, producing a warning like “Prototype mismatch: sub main::head ($) vs none”. Get around this problem by just not importing LWP::Simple’s head function, like so:
use LWP::Simple qw(!head);
use CGI qw(:standard);  # then only CGI.pm defines a head()
Then if you do need LWP::Simple’s head function, you can just call it as LWP::Simple::head($url).

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Prototype mismatch: sub main::head ($) vs none