Different shells have different semantics for setting environment variables. Consider:

#csh/tcsh
setenv PEOPLE 5033

#bash/ksh
export PEOPLE=5033

#sh
PEOPLE=5033
export PEOPLE

#perl
$ENV{PEOPLE} = 5033

As I allude to above, environment variables in perl are stored in a hash called %ENV. You are free to modify this hash as you see fit.