$ perl -E 'say qr{}x'
(?^ux:)
$ perl -E 'say qr{}g'
Unknown regexp modifier "/g" at -e line 1, near "say "
Execution of -e aborted due to compilation errors.
$ perl -E 'say m{}g'

$ perl -E 'say m{}e'
Unknown regexp modifier "/e" at -e line 1, near "say "
Execution of -e aborted due to compilation errors.
$ perl -E 'say s{}{}e'
1