Two easy ways to do this:

• in some versions of cron (linux's vixie cron, for one), there is a facility to just write out the environment at the top of the crontab.
• more robust, and more cross-platform supprted: you can just source your shell rc/profile file before the command in the cron. Example (for bash... substitute your own shell as appropriate):

  0 7 * * *  . ~/.bash_profile ; perl eat_breakfast.pl
  0 12 * * * . ~/.bash_profile ; perl eat_lunch.pl
  0 18 * * * . ~/.bash_profile ; perl eat_dinner.pl
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P.S. (update) This doesn't actually have anything to do with perl... it has to do with how environment variables are set and inherited, and how crond fits in with all that... if you want to see a really clear example of that, just put this in your crontab:

* * * * * env > ~/cron_env
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