BEGIN { *basename = shortcutted { s!.*/!! for @_ }; }

for( '/path/to/foo', '/some/path/to/bar' ) {
	print "Munging " . basename . "\n";
	open my $fh, '<', $_ or die $!;
	# note how $_ still contains the full pathname
	# ...
}

##</code><code>##

sub shortcutted(&) {
	my $sub = shift;
	sub {
		my @byval;
		my $nondestructive = defined wantarray;
		$sub->( $nondestructive
			? ( @byval = @_ ? @_ : $_ )
			: (          @_ ? @_ : $_ )
		);
		return $nondestructive ? @byval[ 0 .. $#byval ] : ();
	};
}

##</code><code>##

use Test::More;

sub original() { 'original' }
sub modified() { 'modified' }

my $test = shortcutted { $_ = modified for @_ };

plan tests => my $num_tests;

{
	local $_ = original;
	$test->();
	is( $_, modified, 'in-place on $_' );
	BEGIN { $num_tests += 1 }
}

{
	local $_ = original;
	my $res = $test->();
	is( $_,   original, 'nondestructive from $_' );
	is( $res, modified, '...returned correctly' );
	BEGIN { $num_tests += 2 }
}

{
	my $num = 10;
	my @original = ( original ) x $num;
	my @modified = ( modified ) x $num;
	$test->( my @data = @original );
	is_deeply( \@data, \@modified, 'in-place on params' );
	BEGIN { $num_tests += 1 }
}

{
	my $num = 10;
	my @original = ( original ) x $num;
	my @modified = ( modified ) x $num;
	my @res = $test->( my @data = @original );
	is_deeply( \@data, \@original, 'non-destructive from params' );
	is_deeply( \@res,  \@modified, '...returned correctly' );
	BEGIN { $num_tests += 2 }
}