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Re^2: Test if a string is a sub name

by BillKSmith (Monsignor)
on Oct 06, 2022 at 15:15 UTC ( [id://11147273] : note . print w/replies, xml ) Need Help??

in reply to Re: Test if a string is a sub name
in thread Test if a string is a sub name

I do not understand how your expression &$string works. The documentation for exists tells us that the expression must return the name of a subroutine. It appears to me that this would only be true for your expression if $string is a symbolic reference (which is prohibited by use strict). I would expect you need string interpolation (perhaps "&$string") but this syntax throws an error that the argument of exists is not a subroutine.

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Re^3: Test if a string is a sub name
by choroba (Cardinal) on Oct 06, 2022 at 15:22 UTC
    It seems the documentation uses the term "subroutine name" in quite a confusing way. Check the examples:
    Use of a subroutine call, rather than a subroutine name, as an argument to exists is an error.
    exists ⊂ # OK exists &sub(); # Error

    So, in this context, "subroutine name" includes the ampersand.

    Considering strict, note the exceptions to strict 'refs':

    $bar = \&{'foo'}; &$bar;
    We are not calling the subroutine, we're just checking it exists/is defined.

    map{substr$_->[0],$_->[1]||0,1}[\*||{},3],[[]],[ref qr-1,-,-1],[{}],[sub{}^*ARGV,3]