If I understand the OP’s question correctly, the programme’s structure is something like this:

#! perl
use strict;
use warnings;

for (qw(literal1 literal2 literal3))
{
    print "$_\n";
    foo('wilma');
}

sub foo
{
    $_ = 'fred';
    goto &bar;
}

sub bar
{
    my ($name) = @_;
    print "foo --> name = $name, \$_ = $_\n";
}

[download]

Unfortunately, changing the line $_ = 'fred'; to local $_ = 'fred'; doesn’t work: it does fix the syntax error, but within sub bar $_ is still literal1, literal2, and literal3 on successive iterations of the for loop. From the documentation for goto (underlining added):

The goto-&NAME form ... exits the current subroutine (losing any changes set by local()) and immediately calls in its place the named subroutine using the current value of @_.

The problem is that on each iteration of the for loop, global $_ is made an alias of the next item in the list. When that argument is a literal, this makes global $_ readonly, and that effect is undone only when that loop iteration completes. There doesn’t appear to be any way to undo this effect. :-(

Athanasius <°(((>< contra mundum Iustus alius egestas vitae, eros Piratica,

In reply to Re^2: How to safely use $_ in a library function? by Athanasius
in thread How to safely use $_ in a library function? by perl-diddler

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