A my
declares the listed variables to be local (lexically) to the enclosing block, file, or eval
. If more than one variable is listed, the list must be placed in parentheses.
Note that with a parenthesised list, undef
can be used as a dummy placeholder, for example to skip assignment of initial values:
my ( undef, $min, $hour ) = localtime;
Redeclaring a variable in the same scope or statement will "shadow" the previous declaration, creating a new instance and preventing access to the previous one. This is usually undesired and, if warnings are enabled, will result in a warning in the shadow
category.
The exact semantics and interface of TYPE and ATTRS are still evolving. TYPE may be a bareword, a constant declared with use constant
, or __PACKAGE__
. It is currently bound to the use of the fields pragma, and attributes are handled using the attributes pragma, or starting from Perl 5.8.0 also via the Attribute::Handlers module. See "Private Variables via my()" in perlsub for details.