sub collect {
    join '', map {
        open my $fh, '<', $_ or warn "Can't open `$_': $!\n";
        <$fh>;
    } @_;
}

##</code><code>##

picard:~/tmp [11:26:38]$ perl -v | head -n 2

This is perl, v5.10.0 built for i486-linux-gnu-thread-multi
picard:~/tmp [11:26:42]$ cat ../domk.pl
#!/usr/bin/perl

use strict;
use warnings;

while (<>) {
    chomp;
    print "huzzah:".collect( $_ )."!\n";
}

sub collect {
    local *ARGV;
    @ARGV = @_;
    join '', <>;
}

__END__
picard:~/tmp [11:26:55]$ ls file? | ../domk.pl
Can't open file1: No such file or directory at ../domk.pl line 14.
huzzah:!
Can't open file2: No such file or directory at ../domk.pl line 14.
huzzah:!
Can't open : No such file or directory at ../domk.pl line 14.
huzzah:!

##</code><code>##

#!/usr/bin/perl

use strict;
use warnings;
use Test::More 'no_plan';

sub dargv {
    local *ARGV;
    @ARGV = @_;
    <>;
}

sub dopen {
    map {
        open my $fh, '<', $_ or warn "Can't open `$_': $!\n";
        <$fh>;
    } @_;
}

while (<>) {
    chomp;
    is_deeply [dargv $_], [dopen $_] => $_;
}

__END__