> What does $ stand for in the following statement?
>
> print"$_\t", "*" x $n, "\n";
>
$_ is the default input and pattern-searching space.
Snipped from man perlvar:
PERLVAR(1) Perl Programmers Reference Guide PERLVAR(1)
NAME
perlvar - Perl predefined variables
DESCRIPTION
Predefined Names
The following names have special meaning to Perl. Most
punctuation names have reasonable mnemonics, or analogs in
the shells. Nevertheless, if you wish to use long vari
able names, you need only say
$ARG
$_ The default input and pattern-searching space.
The following pairs are equivalent:
while (<>) {...} # equivalent only in while!
while (defined($_ = <>)) {...}
/^Subject:/
$_ =~ /^Subject:/
tr/a-z/A-Z/
$_ =~ tr/a-z/A-Z/
chomp
chomp($_)
Here are the places where Perl will assume $_ even
if you don't use it:
Various unary functions, including functions
like ord() and int(), as well as the all file
tests ("-f", "-d") except for "-t", which
defaults to STDIN.
Various list functions like print() and
unlink().
The pattern matching operations "m//", "s///",
and "tr///" when used without an "=~" operator.
The default iterator variable in a "foreach"
loop if no other variable is supplied.
The implicit iterator variable in the grep()
and map() functions.
The default place to put an input record when a
"<FH>" operation's result is tested by itself
as the sole criterion of a "while" test. Out
side a "while" test, this will not happen.
(Mnemonic: underline is understood in certain
operations.)
HTH,
-tir
--
Tirthankar, IGIDR.
+91-22-8400919 x275 (r), x593(o), x(542),
+91-22-8421206 (r)
http://www.igidr.ac.in/~tir
XL
Could we forget the widow'd hour
And look on Spirits breathed away,
As on a maiden in the day
When first she wears her orange-flower!
-Tennyson, Lord Alfred. (In Memoriam A.H.H.)
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