Re^2: What is the scope of $_?

[Lotus1]

in reply to Re: What is the scope of $_?
in thread What is the scope of $_?

If all the OP's examples use the global $_ then printing it at the end would show the last value assigned. What actually happens is a warning for 'Use of uninitialized value $_ ...' The subroutine uses whatever $_ that is in scope when it is called.

use warnings;
use strict;

sub abc()
{
  $_ = 'x';
}

foreach(1..2)
{
    my $loopvar = 'in the loop';
  print "Before:$_\n";
  abc();
  print "After:$_\n";
}

print "\$_ = $_\n";  # warning for uninitialized value $_ (global scop
+e)

abc();
print "\$_ = $_\n";  # prints $_ = x

[tobyink]

As I said, all the OP's examples use the global $_ but some Perl control structures localize that variable.

The same effect is illustrated here using global $::x...

use warnings;
use strict;

sub abc()
{
    $::x = 'x';
}

foreach $::x (1..2)
{
    print "Before:$::x\n";
    abc();
    print "After:$::x\n";
}

print "\$::x = $::x\n";  # warning for uninitialized value $x (global 
+scope)

abc();
print "\$::x = $::x\n";  # prints $x = x

[Lotus1]

So when the foreach loop finishes it restores the undef value to $_. Thanks.