$ for num in $( seq 1 3 ); do perl print_env_num.pl; done
$ for num in $( seq 1 3 ); do export num;  perl print_env_num.pl; done
1
2
3
$ cat print_env_num.pl
#!/usr/bin/perl -l
# vim: set ts=4 sw=4 et sta:
use strict;
use warnings;

print $ENV{num} if exists $ENV{num};