Bryan Harris wrote:
Is it not possible to use $_ in subroutines?
Yes it is, just not the way you seem to want to use it.
For example, my temptation was to do this:
**************************************
sub isDate {
$_ = shift;
if (m!\d{2}/\d{2}/\d{2}!) { return 1; }
else { return 0; }
}
Why is this in a subroutine at all? If you are using it like:
if ( isDate() ) { #use $_ by default
Then just do this instead:
if ( m!\d{2}/\d{2}/\d{2}! ) {
Or use a variable instead:
my $isDate = qr!\d{2}/\d{2}/\d{2}!;
...
if ( /$isDate/ ) {
**************************************
... but by modifying $_ I was clobbering $_ elsewhere in the larger program!
Yes because $_ is a special global variable. This effect is called
"action at a distance" which is why it is better to use named lexically
scoped variables instead of $_.
Oddly, perl won't let me do "my ($_) = shift;", so I'm stuck having to use
another variable.
Perl 5.10 *will* let you do "my $_".
Why can't we do that? Is using $_ in subroutines discouraged??
Yes, precisely for the problems that you discovered.
John
--
Those people who think they know everything are a great
annoyance to those of us who do. -- Isaac Asimov
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