Not that I like the idea, but if.pm can do this. use if (not grep {/--nostrict/} @ARGV), 'strict'; if.pm ships with recent perl, but works with long-gone ones too, where it can be installed from CPAN.

Added - You should use Getopt::Long or something to remove that flag from @ARGV before you start processing input files. With a $nostrict flag set by that, your users can take advantage of all that freedom with things like,

goto I_LIKE_MY_VARIABLES_STEALTHED_AND_GLOBAL if $nostrict;
my ($foo, @bar, %baz);
I_LIKE_MY_VARIABLES_STEALTHED_AND_GLOBAL:
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I'm a little puzzled, btw. What sort of perl programs are you providing your users that they have to care about strict or even know about it?