There is an easy way.

>perl -wle "BEGIN { require CGI; CGI->VERSION(100) };"
CGI version 100 required--this is only version 3.15 at -e line 1.
BEGIN failed--compilation aborted at -e line 1.
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Also, Exporter emulates this behaviour, so your code would have worked if CGI used Exporter.

>perl -e"{ package Mod; $VERSION='3.15'; } Mod->import(100)"

>perl -e"{ package Mod; $VERSION='3.15'; use Exporter; @ISA='Exporter'
+; } Mod->import(100)"
Mod version 100 required--this is only version 3.15 at c:/Progs/perl58
+8/lib/Exporter/Heavy.pm line 121.
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