C:\chas_sandbox>
perl -Mdiagnostics -le "sub doit{$ref=$_;${$ref} = 'nope'};$str='cwh';print $str
;doit(\$str);print$str"
cwh
cwh

C:\chas_sandbox>
perl -Mdiagnostics -le "sub doit{$ref=$_;${$ref} = 'nope'};$str='cwh';print $str
;doit(\\$str);print$str"
cwh
cwh

C:\chas_sandbox>
perl -Mdiagnostics -le "sub doit{$ref=$_;$$ref = 'nope'};$str='cwh';print $str;d
oit(\\$str);print$str"
cwh
cwh

C:\chas_sandbox>
perl -Mdiagnostics -le "sub doit{$ref=$_;$$ref = 'nope'};$str='cwh';print $str;d
oit(\$str);print$str"
cwh
cwh

C:\chas_sandbox>