Hi rsmah++,

That is a very interesting question!

I don't know if this is the best answer, but my first thought was to try assigning to the variable and see what happens: 

use strict;
use warnings;

my $a = "123";
foo($a, "456");

sub foo {
    for (my $i = 0; $i < @_; $i++) {
        my $type = eval { $_[$i] = "variable" } || "constant";
        printf "Arg #%d is $type\n", $i + 1;
    }
}

[download]

The output of this is: 

Arg #1 is variable
Arg #2 is constant

[download]

Since the write operation is wrapped in an eval, it returns undef if the assignment failed (constant), otherwise the result of the assignment.

s''(q.S:$/9=(T1';s;(..)(..);$..=substr+crypt($1,$2),2,3;eg;print$..$/

In reply to Re: How do you tell if a sub argument is an lvalue? by liverpole
in thread How do you tell if a sub argument is an lvalue? by rsmah

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